This flag was added to binutils/ld in the 2.30 release,
see commit c11c786f0b45617bb8807ab6a57220d5ff50e414:
> The new "-z separate-code" option will generate separate code LOAD
segment which must be in wholly disjoint pages from any other data.
It was made the default for Linux/x86 targets in the 2.31 release, see commit
f6aec96dce1ddbd8961a3aa8a2925db2021719bb:
> This patch adds --enable-separate-code to ld configure to turn on
-z separate-code by default and enables it by default for Linux/x86.
This avoids mixing code pages with data to improve cache performance
as well as security.
> To reduce x86-64 executable and shared object sizes, the maximum page
size is reduced from 2MB to 4KB when -z separate-code is turned on by
default. Note: -z max-page-size= can be used to set the maximum page
size.
> We compared SPEC CPU 2017 performance before and after this change on
Skylake server. There are no any significant performance changes.
Everything is mostly below +/-1%.
Support was also added to LLVMs lld: https://reviews.llvm.org/D64903, however
there is remains off by default.
There were concerns about an increase in binary size, however in our case, the
increase (1 page worth of bytes) would seem negligible, given we are shipping a
multi-megabyte binary, which then downloads 100's of GBs of data.
Also note that most recent versions of distros are shipping a new enough version
of binutils that this is available and/or on by default (assuming the distro has
not turned it off, I haven't checked everywhere):
CentOS 8: 2.30
Debian Buster 2.31.1
Fedora 29: 2.31.1
FreeBSD: 2.33
GNU Guix: 2.33 / 2.34
Ubuntu 18.04: 2.30
Related threads / discussion:
https://bugzilla.redhat.com/show_bug.cgi?id=1623218
While testing #19530 I noticed that we couldn't call dsymutil after LTO:
```bash
../libtool: line 10643: x86_64-apple-darwin16-dsymutil: command not found
```
This updates configure to call `AC_PATH_TOOL` so that we end up with the
full path to dsymutil, similar to `otool` and `install_name_tool`, ie:
`/bitcoin/depends/x86_64-apple-darwin16/share/../native/bin/x86_64-apple-darwin16-otool`.
Debian GCC ignores -Wformat-security, without -Wformat, which
means when we test for it, it currently fails:
```bash
checking whether C++ compiler accepts -Wformat-security... no
...
configure:15907: checking whether C++ compiler accepts -Wformat-security
configure:15926: g++ -std=c++11 -c -g -O2 -Werror -Wformat-security conftest.cpp >&5
cc1plus: error: '-Wformat-security' ignored without '-Wformat' [-Werror=format-security]
cc1plus: all warnings being treated as errors
```
Fix this by just combining the -Wformat and -Wformat-security checks
together.
92bc268e4a build: Detect missed pkg-config early (Hennadii Stepanov)
1739eb23d8 build: Drop unused use_pkgconfig variable (Hennadii Stepanov)
a661449a2e build: Drop use_pkgconfig check for libmultiprocess check (Hennadii Stepanov)
90b95e7929 build: Drop dead non-pkg-config code for libevent check (Hennadii Stepanov)
44a14afbb8 build: Drop dead non-pkg-config code for qrencode check (Hennadii Stepanov)
10cbae0c39 build: Drop dead non-pkg-config code for ZMQ check (Hennadii Stepanov)
06cfc9cadf build: Fix indentation in UNIVALUE check (Hennadii Stepanov)
6fd2118e77 build: Drop dead non-pkg-config code for UNIVALUE check (Hennadii Stepanov)
e9edbe4dbd build: Always use pkg-config (Hennadii Stepanov)
9e2e753b06 build: Always define ZMQ_STATIC for MinGW (Hennadii Stepanov)
Pull request description:
This PR:
- is based on #18297 (already merged)
- drops all of the non-pkg-config paths from the `configure` script
Ref: #17768
ACKs for top commit:
fanquake:
ACK 92bc268e4a. I re-gitian-built. There are a couple follow-ups that I'll PR shortly. Thanks for addressing my feedback above. I took too long to get back to this.
laanwj:
ACK 92bc268e4a
Tree-SHA512: 83c2d9cf03518867a1ebf7e26a8fc5b6dd8962ef983fe0d84e0c7eb74717f4c36a834da02faf0e503ffd87167005351671cf040c0d4ddae57ee152a6ff84012b
c4ffcf07af build: remove BIP70 configure option (fanquake)
Pull request description:
This was left in after #17165, so that anyone who had been compiling
with (already disabled by default) BIP70 would realise that support
had been completely removed in 0.20.0. However we should be able to
remove it for 0.21.0.
ACKs for top commit:
jnewbery:
utACK c4ffcf07af
MarcoFalke:
ACK c4ffcf07af with or without the "catch-all reject"
Tree-SHA512: a5dd4231ed97c9dd1984fb90d69a8725df2fdda0b963269b0575601c74528e5d820a4a863c428f8ede86eaae2a1606671fe1fcebdeb96b1023f7a5f899270284
9952242c03 build: improve builtin_clz* detection (fanquake)
Pull request description:
Fixes#19402.
The way we currently test for `__builtin_clz*` support with `AC_CHECK_DECLS` does not work with Clang:
```bash
configure:21492: clang++-10 -std=c++11 -c -g -O2 -DHAVE_BUILD_INFO -D__STDC_FORMAT_MACROS conftest.cpp >&5
conftest.cpp💯10: error: builtin functions must be directly called
(void) __builtin_clz;
^
1 error generated.
```
This also removes the `__builtin_clz()` check, as we don't actually use it anywhere, and it's trvial to re-add detection if we do start using it at some point. If this is controversial then I'll add a test for it as well.
ACKs for top commit:
sipa:
ACK 9952242c03
laanwj:
ACK 9952242c03
Tree-SHA512: 695abb1a694a01a25aaa483b4fffa7d598842f2ba4fe8630fbed9ce5450b915c33bf34bb16ad16a16b702dd7c91ebf49fe509a2498b9e28254fe0ec5177bbac0
The way we currently test with AC_CHECK_DECLS do not work with Clang:
```bash
configure:21492: clang++-10 -std=c++11 -c -g -O2 -DHAVE_BUILD_INFO -D__STDC_FORMAT_MACROS conftest.cpp >&5
conftest.cpp💯10: error: builtin functions must be directly called
(void) __builtin_clz;
^
1 error generated.
```
This also removes the __builtin_clz() check, as we don't actually use
it anywhere, and it's trvial to re-add detection if we do start using
it at some point.
On OS X, when searching Homebrew keg-only packages for BDB 4.8, if we find it,
use BDB_CPPFLAGS and BDB_LIBS instead of CFLAGS and LIBS for the result. This
is (1) more correct, and (2) necessary in order to give this location
priority over other directories in the include search path, which may include
system include directories with other versions of BDB.
This option causes the compiler to insert probes whenever stack space
is allocated statically or dynamically to reliably detect stack overflows
and thus mitigate the attack vector that relies on jumping over a stack
guard page as provided by the operating system.
This option is now enabled by default in Ubuntu GCC as of 19.10.
Available in GCC 8 and Clang 11.
8a26848c46 build: Fix m4 escaping (Hennadii Stepanov)
9123ec15db build: Remove extra tokens warning (Hennadii Stepanov)
fded4f48c3 build: Remove duplicated QT_STATICPLUGIN define (Hennadii Stepanov)
05a93d5d96 build: Fix indentation in bitcoin_qt.m4 (Hennadii Stepanov)
ddbb419310 build: Use pkg-config in BITCOIN_QT_CONFIGURE for all hosts (Hennadii Stepanov)
492971de35 build: Fix mingw pkgconfig file and dependency naming (Hennadii Stepanov)
Pull request description:
This PR makes `bitcoin_qt.m4` to use `pkg-config` for all hosts and removes non-pkg-config paths from it. This is a step towards the idea which was clear [stated](https://github.com/bitcoin/bitcoin/pull/8314#issue-76644643) by Cory Fields:
> I believe the consensus is to treat Windows like the others and require pkg-config across the board. We can drop all of the non-pkg-config paths, and simply AC_REQUIRE(PKG_PROG_PKG_CONFIG)
There are two unsolved problems with this PR. If depends is built with `DEBUG=1` the `configure` script fails to pickup Qt:
- for macOS host (similar to, but not the same as #16391)
- for Windows host (regression)
The fix is ~on its way~ submitted in #18298 (as a followup).
Also this PR picks some small improvements from #17820.
ACKs for top commit:
theuni:
Code review ACK 8a26848c46
dongcarl:
Code Review ACK 8a26848c46
laanwj:
Code review ACK 8a26848c46
Tree-SHA512: 3b25990934b939121983df7707997b31d61063b1207d909f539d69494c7cb85212f353092956d09ecffebb9fef28b869914dd1216a596d102fcb9744bb5487f7
This was left in after #17165, so that anyone who had been compiling
with (already disabled by default) BIP70 would realise that support
had been completely removed in 0.20.0. However we should be able to
remove it for 0.21.0.
Fuzzing code uses C++17 specific code (e.g. std::optional), so it is not
possible to compile with --enable-fuzz and without --enable-c++17.
Thus, turn on --enable-c++17 whenever --enable-fuzz is used.
eea8114657 build: Enable unreachable-code-loop-increment (Jonathan Schoeller)
d15db4b1fc refactor: Fix unreachable code in init arg checks (Jonathan Schoeller)
Pull request description:
Closes: #19017
In #19015 it's been suggested that we add some new compiler warnings to our build. Some of these, such as `-Wunreachable-code-loop-increment`, generate warnings. We'll likely want to fix these up if we're going to turn these warnings on.
```shell
init.cpp:969:5: warning: loop will run at most once (loop increment never executed) [-Wunreachable-code-loop-increment]
for (const auto& arg : gArgs.GetUnsuitableSectionOnlyArgs()) {
^~~
1 warning generated.
```
aa8d76806c/src/init.cpp (L968-L972)
To fix this, collect all errors, and output them in a single error message after the loop completes. This resolves the unreachable code warning, and avoids popup hell that could result from outputting a seperate message for each error or warning one by one.
ACKs for top commit:
laanwj:
Code review ACK eea8114657
hebasto:
re-ACK eea8114657, only suggested changes applied since the [previous](https://github.com/bitcoin/bitcoin/pull/19131#pullrequestreview-421772387) review.
Tree-SHA512: 2aa3ceb7fab581b6ba2580900668388d8eba1c3001c8ff9c11c1f4a9a10fbc37f30e590249862676858446e3f4950140a252953ba1643ba3bfd772f8eae20583
facef3d413 doc: Explain that anyone can work on good first issues, move text to CONTRIBUTING.md (MarcoFalke)
fae2fb2a19 doc: Expand section on Getting Started (MarcoFalke)
100000d1b2 doc: Add headings to CONTRIBUTING.md (MarcoFalke)
fab893e0ca doc: Fix unrelated typos reported by codespell (MarcoFalke)
Pull request description:
Some random doc changes:
* Add sections to docs, so that they can be linked to
* Explain that anyone (even maintainers) are allowed to work on good first issues
* Expand section on Getting Started slightly
ACKs for top commit:
hebasto:
ACK facef3d413
fanquake:
ACK facef3d413
Tree-SHA512: 8998e273a76dbf4ca77e79374c14efe4dfcc5c6df6b7d801e1e1e436711dbe6f76b436f9cbc6cacb45a56827babdd6396f3bd376a9426ee7be3bb9b8a3b8e383
While emoji and other symbols in C++ identifers (as accepted by newer
compilers) are fun, they might create confusion during code review, for
example because some symbols look very similar. Forbid such extended
identifiers for now.
This is done by providing `-fno-extended-identifiers`. Thanks to sipa
for suggesting this compiler flag.
e2bab2aa16 multiprocess: add multiprocess travis configuration (Russell Yanofsky)
603fd6a2e7 depends: add MULTIPROCESS depends option (Russell Yanofsky)
5d1377b52b build: multiprocess autotools changes (Russell Yanofsky)
Pull request description:
This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/projects/10).
---
This PR consists of build changes only. It adds an `--enable-multiprocess` autoconf option (off by default and marked experimental), that builds new `bitcoin-node` and `bitcoin-gui` binaries. These currently function the same as existing `bitcoind` and `bitcoin-qt` binaries, but are extended in #10102 with IPC features to execute node, wallet, and gui functions in separate processes.
In addition to adding the `--enable-multiprocess` config flag, it also adds a depends package and autoconf rules to build with the [libmultiprocess](https://github.com/chaincodelabs/libmultiprocess) library, and it adds new travis configuration to exercise the build code and run functional tests with the new binaries.
The changes in this PR were originally part of #10102 but were moved into #16367 to be able to develop and review the multiprocess build changes independently of the code changes. #16367 was briefly merged and then reverted in #18588. Only change since #16367 has been dropping the `native_boost.mk` depends package which was pointed out to be no longer necessary in https://github.com/bitcoin/bitcoin/pull/16367#issuecomment-596484337 and https://github.com/bitcoin/bitcoin/pull/18588#pullrequestreview-391765649
ACKs for top commit:
practicalswift:
ACK e2bab2aa16
Sjors:
tACK e2bab2aa16 on macOS 10.15.4
hebasto:
ACK e2bab2aa16, tested on Linux Mint 19.3 (x86_64):
Tree-SHA512: b5a76eab5abf63d9d8b6d628cbdff4cc1888eef15cafa0a5d56369e2f9d02595fed623f4b74b2cf2830c42c05a774f0943e700f9c768a82d9d348cad199e135c
Instruct the linker to set the major & minor subsystem versions in the PE
header to 6 & 1 (NT 6.1 which corresponds to Windows 7). Similar to
macOS, the binary will now refuse to run on unsupported versions of
Windows.
a30b0a24e9 build: enable -Werror=gnu (Vasil Dimov)
Pull request description:
Stop the build if a warning is emitted due to `-Wgnu` and
`--enable-werror` has been used. As usual - this would help notice such
a warning that is about to be introduced in new code.
This is a followup to
https://github.com/bitcoin/bitcoin/pull/18088 build: ensure we aren't using GNU extensions
ACKs for top commit:
practicalswift:
ACK a30b0a24e9
Empact:
ACK a30b0a24e9
Tree-SHA512: f81b71cf3ee4db88b6f664c571075e0d30800a604f067f44273f256695a1dea533779db2ac859dd0a4cd8b66289c3e45f4aff1cfadfa160a1c354237167b05e2
df6bde031b test: remove glibc fdelt sanity check (fanquake)
8bf1540cc2 build: remove fdelt_chk backwards compatibility code (fanquake)
Pull request description:
ae30d40e50
The return type of [`fdelt_chk`](https://sourceware.org/git/?p=glibc.git;a=blob;f=debug/fdelt_chk.c;h=f62ce7349707cb68f55831c1c591fd7387a90258;hb=HEAD) changed from `unsigned long int` to `long int` in glibc 2.16. See [this commit](https://sourceware.org/git/?p=glibc.git;a=commit;h=ceb9e56b3d1f8c1922e0526c2e841373843460e2). Now that we require [glibc >=2.17](https://github.com/bitcoin/bitcoin/pull/17538) we can remove our back-compat code.
ab7bce584a
While looking at the above changes, I noticed that our glibc fdelt sanity check doesn't seem to be checking anything. `fdelt_warn()` also isn't something we'd want to actually "trigger" at runtime, as doing so would cause `bitcoind` to abort.
The comments:
> // trigger: Call FD_SET to trigger __fdelt_chk. FORTIFY_SOURCE must be defined
> // as >0 and optimizations must be set to at least -O2.
suggest calling FD_SET to check the invocation of `fdelt_chk` (this is [aliased with fdelt_warn in glibc](https://sourceware.org/git/?p=glibc.git;a=blob;f=debug/fdelt_chk.c;h=f62ce7349707cb68f55831c1c591fd7387a90258;hb=HEAD)). However just calling `FD_SET()` will not necessarily cause the compiler to insert a call to `fd_warn()`.
Whether or not GCC (recent Clang should work, but may use different heuristics) inserts a call to `fdelt_warn()` depends on if the compiler can determine if the value passed in is a compile time constant (using [`__builtin_constant_p`](https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html)) and whether the value is < 0 or >= `FD_SETSIZE`. The glibc implementation is [here](https://sourceware.org/git/?p=glibc.git;a=blob;f=misc/bits/select2.h;h=7e17430ed94dd1679af10afa3d74795f9c97c0e8;hb=HEAD). This means our check should never cause a call to be inserted.
Compiling master without `--glibc-back-compat` (if you do pass `--glibc-back-compat` the outcome is still the same; however the abort will only happen with >=`FD_SETSIZE` as that is what our [fdelt_warn()](https://github.com/bitcoin/bitcoin/blob/master/src/compat/glibc_compat.cpp#L24) checks for), there are no calls to `fdelt_warn()` inserted by the compiler:
```bash
objdump -dC bitcoind | grep sanity_fdelt
...
0000000000399d20 <sanity_test_fdelt()>:
399d20: 48 81 ec 98 00 00 00 sub $0x98,%rsp
399d27: b9 10 00 00 00 mov $0x10,%ecx
399d2c: 64 48 8b 04 25 28 00 mov %fs:0x28,%rax
399d33: 00 00
399d35: 48 89 84 24 88 00 00 mov %rax,0x88(%rsp)
399d3c: 00
399d3d: 31 c0 xor %eax,%eax
399d3f: 48 89 e7 mov %rsp,%rdi
399d42: fc cld
399d43: f3 48 ab rep stos %rax,%es:(%rdi)
399d46: 48 8b 84 24 88 00 00 mov 0x88(%rsp),%rax
399d4d: 00
399d4e: 64 48 33 04 25 28 00 xor %fs:0x28,%rax
399d55: 00 00
399d57: 75 0d jne 399d66 <sanity_test_fdelt()+0x46>
399d59: b8 01 00 00 00 mov $0x1,%eax
399d5e: 48 81 c4 98 00 00 00 add $0x98,%rsp
399d65: c3 retq
399d66: e8 85 df c8 ff callq 27cf0 <__stack_chk_fail@plt>
399d6b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
```
If you modify the sanity test to pass `-1` or `FD_SETSIZE` to `FD_SET`, you'll see calls to `fdelt_warn` inserted, and the runtime behaviour is an abort as expected.
```diff
diff --git a/src/compat/glibc_sanity_fdelt.cpp b/src/compat/glibc_sanity_fdelt.cpp
index 87140d0c7..16974bfa0 100644
--- a/src/compat/glibc_sanity_fdelt.cpp
+++ b/src/compat/glibc_sanity_fdelt.cpp
@@ -20,7 +20,7 @@ bool sanity_test_fdelt()
{
fd_set fds;
FD_ZERO(&fds);
- FD_SET(0, &fds);
+ FD_SET(FD_SETSIZE, &fds);
return FD_ISSET(0, &fds);
}
#endif
```
```bash
0000000000399d20 <sanity_test_fdelt()>:
399d20: 48 81 ec 98 00 00 00 sub $0x98,%rsp
399d27: b9 10 00 00 00 mov $0x10,%ecx
399d2c: 64 48 8b 04 25 28 00 mov %fs:0x28,%rax
399d33: 00 00
399d35: 48 89 84 24 88 00 00 mov %rax,0x88(%rsp)
399d3c: 00
399d3d: 31 c0 xor %eax,%eax
399d3f: 48 89 e7 mov %rsp,%rdi
399d42: fc cld
399d43: f3 48 ab rep stos %rax,%es:(%rdi)
399d46: 48 c7 c7 ff ff ff ff mov $0xffffffffffffffff,%rdi
399d4d: e8 3e ff ff ff callq 399c90 <__fdelt_warn>
399d52: 0f b6 04 24 movzbl (%rsp),%eax
399d56: 83 e0 01 and $0x1,%eax
399d59: 48 8b 94 24 88 00 00 mov 0x88(%rsp),%rdx
399d60: 00
399d61: 64 48 33 14 25 28 00 xor %fs:0x28,%rdx
399d68: 00 00
399d6a: 75 08 jne 399d74 <sanity_test_fdelt()+0x54>
399d6c: 48 81 c4 98 00 00 00 add $0x98,%rsp
399d73: c3 retq
399d74: e8 77 df c8 ff callq 27cf0 <__stack_chk_fail@plt>
399d79: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
```
```bash
src/bitcoind
*** buffer overflow detected ***: src/bitcoind terminated
Aborted
```
I think the test should should be removed and replaced (if possible) with additional checks in security-check.py. I was thinking about adding a version of [this script](https://github.com/fanquake/core-review/blob/master/fortify.py) as part of the output, but that needs more thought. I'll address this in a follow up.
ACKs for top commit:
laanwj:
ACK df6bde031b
Tree-SHA512: d8b3af4f4eb2d6c767ca6e72ece51d0ab9042e1bbdfcbbdb7ad713414df21489ba3217662b531b8bfdac0265d2ce5431abfae6e861b6187d182ff26c6e59b32d
0c63f80854 build: Suppress -Wdeprecated-copy warnings (Hennadii Stepanov)
Pull request description:
Tomorrow, on Apr 23 the Ubuntu 20.04 release is expected. It packaged with Qt 5.12 LTS that has a nasty peculiarity to cause modern compilers, including Clang 10.0 and GCC 9.3, to emit spammy `-Wdeprecated-copy` warnings (#15822, #18419).
This PR suppress such warnings _temporarily_, until the [upstream is fixed](https://codereview.qt-project.org/c/qt/qtbase/+/272258).
Here are some affected systems (with system packages):
- Ubuntu 20.04 LTS + Qt 5.12.8 LTS + { Clang 10.0 | GCC 9.3 }
- Fedora 32 + Qt 5.13.2 + Clang 10.0
Reference: [QTBUG-75210](https://bugreports.qt.io/browse/QTBUG-75210)
Also see **fanquake**'s [comment](https://github.com/bitcoin/bitcoin/pull/18738#issuecomment-622956100).
ACKs for top commit:
MarcoFalke:
ACK 0c63f80854 seems fine to disable this warning for the 0.21.0 release temporarily and then enable it for 0.22.0, when boost is removed.
fanquake:
ACK 0c63f80854 - I think it's ok to suppress these for now, given that `-Wdeprecated-copy` is enabled (via `-Wextra`) in GCC 9 and Clang 10. The Qt output is pretty noisy, and there's a few warnings from Boost as well.
Tree-SHA512: 7064a3272bc9eae00b73a16c421ac58be148f374cbef87320e8f092f52761f6e98166eff60346b70867f8a69a9698a79455dc16b42d92f8fbe7c56519571ac08
839add193b build: Enable -Wsuggest-override (Hennadii Stepanov)
de5e91c303 refactor: Add BerkeleyDatabaseVersion() function (Hennadii Stepanov)
Pull request description:
From GCC [docs](https://gcc.gnu.org/onlinedocs/gcc-9.2.0/gcc/Warning-Options.html):
> `-Wsuggest-override`
> Warn about overriding virtual functions that are not marked with the override keyword.
~This PR is based on #16722 (the first commit).~ See: https://github.com/bitcoin/bitcoin/pull/16722#issuecomment-584111086
ACKs for top commit:
fanquake:
ACK 839add193b
vasild:
ACK 839add193
practicalswift:
ACK 839add193b assuming Travis is happy: patch looks correct
Tree-SHA512: 1e8cc085da30d41536deff9b181962c1882314ab252c2ad958294087ae1e5a0dfa4886bdbe36f21cf6ae71df776a8420f349f007d4b5b49fd79ba98ce308965a
autoconf and automake changes to support multiprocess gui/node/wallet execution.
This adds a new --enable-multiprocess flag, and build configuration code to
detect libraries needed for multiprocess support. The --enable-multiprocess
flag builds new bitcoin-node and bitcoin-gui executables, which are updated in
https://github.com/bitcoin/bitcoin/pull/10102 to communicate across processes.
But for now they are functionally equivalent to existing bitcoind and
bitcoin-qt executables.
89fea68ffd build: don't pass -w when building for Windows (fanquake)
Pull request description:
This has been around since the introduction of autotools. However at
this point I'm not sure we'd ever want to suppress all warnings when
performing a build, and given that CXX FLAGS will have been overriden
when cross-compiling for Windows (using depends), this would rarely,
if-ever be used anyways.
From https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html:
> -w
>
> Inhibit all warning messages.
ACKs for top commit:
hebasto:
ACK 89fea68ffd
Tree-SHA512: 2b5bdef7fff5c87b28199f5822cab3cdf600c90c01a40db5cd85053eef5dcb5816e2e97ff61a30ff94b4f0c6cb7be22beaef34d82235bdf05ff9da865d40b381
This has been around since the introduction of autotools. However at
this point I'm not sure we'd every want to suppress all warnings when
performing a build, and given that CXX FLAGS will have been overriden
when cross-compiling for Windows (using depends), this would rarely,
if-ever be used anyways.
From https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html:
-w
Inhibit all warning messages.
As is, this sanity check doesn't seem to be testing fdelt_chk, because
passing a value of "0" to FD_SET wont cause the compiler to insert any
calls to fdelt_chk().
The documentation is a little misleading. If we actually triggered fdelt_chk
at runtime, bitcoind would abort. I think this check would be better replaced
(if possible) by additional checks in security-check.py.
The compiler may insert a call to fdelt_warn() (aliased with fdelt_chk
in glibc) at compile time if it can determine that an invalid value is
being passed to FD_SET.
These checks are essentially; value < 0 or value >= FD_SETSIZE along
with a check for wether the value is a compile time constant.
If the compiler can determine an invalid value is being passed, a call
to fdelt_warn will be inserted. Passing 0 should never cause a call to
be inserted.
You can check this after compiling:
```bash
objdump -dC bitcoind | grep sanity_fdelt
...
0000000000399d20 <sanity_test_fdelt()>:
399d20: 48 81 ec 98 00 00 00 sub $0x98,%rsp
399d27: b9 10 00 00 00 mov $0x10,%ecx
399d2c: 64 48 8b 04 25 28 00 mov %fs:0x28,%rax
399d33: 00 00
399d35: 48 89 84 24 88 00 00 mov %rax,0x88(%rsp)
399d3c: 00
399d3d: 31 c0 xor %eax,%eax
399d3f: 48 89 e7 mov %rsp,%rdi
399d42: fc cld
399d43: f3 48 ab rep stos %rax,%es:(%rdi)
399d46: 48 8b 84 24 88 00 00 mov 0x88(%rsp),%rax
399d4d: 00
399d4e: 64 48 33 04 25 28 00 xor %fs:0x28,%rax
399d55: 00 00
399d57: 75 0d jne 399d66 <sanity_test_fdelt()+0x46>
399d59: b8 01 00 00 00 mov $0x1,%eax
399d5e: 48 81 c4 98 00 00 00 add $0x98,%rsp
399d65: c3 retq
399d66: e8 85 df c8 ff callq 27cf0 <__stack_chk_fail@plt>
399d6b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
```
To test, you could modify this test to pass -1 to FD_SET, and check
that a call to fdelt_warn() is inserted, and that running bitcoind
fails. i.e:
```bash
0000000000399d20 <sanity_test_fdelt()>:
399d20: 48 81 ec 98 00 00 00 sub $0x98,%rsp
399d27: b9 10 00 00 00 mov $0x10,%ecx
399d2c: 64 48 8b 04 25 28 00 mov %fs:0x28,%rax
399d33: 00 00
399d35: 48 89 84 24 88 00 00 mov %rax,0x88(%rsp)
399d3c: 00
399d3d: 31 c0 xor %eax,%eax
399d3f: 48 89 e7 mov %rsp,%rdi
399d42: fc cld
399d43: f3 48 ab rep stos %rax,%es:(%rdi)
399d46: 48 c7 c7 ff ff ff ff mov $0xffffffffffffffff,%rdi
399d4d: e8 3e ff ff ff callq 399c90 <__fdelt_warn>
399d52: 0f b6 04 24 movzbl (%rsp),%eax
399d56: 83 e0 01 and $0x1,%eax
399d59: 48 8b 94 24 88 00 00 mov 0x88(%rsp),%rdx
399d60: 00
399d61: 64 48 33 14 25 28 00 xor %fs:0x28,%rdx
399d68: 00 00
399d6a: 75 08 jne 399d74 <sanity_test_fdelt()+0x54>
399d6c: 48 81 c4 98 00 00 00 add $0x98,%rsp
399d73: c3 retq
399d74: e8 77 df c8 ff callq 27cf0 <__stack_chk_fail@plt>
399d79: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
```
```bash
./src/bitcoind
*** buffer overflow detected ***: src/bitcoind terminated
Aborted
```
a029805f57 build: remove -Qunused-arguments workaround for clang + ccache (fanquake)
Pull request description:
This was added in 386efb7695 to address spammy Clang warnings when building with ccache.
The issue was addressed in [ccache 3.2](https://bugzilla.samba.org/show_bug.cgi?id=8118), and from a look at most major distros, it's only Debian Jessie that has a version of ccache older than that ([3.1](https://packages.debian.org/jessie/ccache)).
Therefore I think it's acceptable to drop this workaround, and re-enable warnings for unused driver arguments (when compiling using Clang and ccache).
ACKs for top commit:
hebasto:
ACK a029805f57.
vasild:
utACK a029805f57
Tree-SHA512: f887b9bd12f9c1c8d209943b86e8dafe33cfd1572912f2cafabe08ffe403973e48f0f7289280a8c6db9263c57aad43fbd4bb72f42db762eb090f3b1ef0538f43
03da4c7781 build: make linker checks more robust (Cory Fields)
Pull request description:
Check for a flag to turn linker warnings into errors. When flags are passed to
linkers via the compiler driver using a -Wl,-foo flag, linker warnings may be
swallowed rather than bubbling up.
This is one of [Corys commits](b9acd3d33e) that I've modified to also add `-Wl,-fatal_warnings`
for darwin.
ACKs for top commit:
vasild:
re-ACK 03da4c778
Tree-SHA512: 212031d619ed88e52aaae30cf3b711681d72c4d670884406403605d1d86c784c84cb07e2e0d6c30926e659db8f14f8dabd5af3de5291637f8080d6dfee358248
71f183a49b build: warn on potentially uninitialized reads (Vasil Dimov)
Pull request description:
* Enable `conditional-uninitialized` warning class to show potentially uninitialized
reads.
* Fix the sole such warning in Bitcoin Core in `GetRdRand()`: `r1` would be
set to `0` on `rdrand` failure, so initializing it to `0` is a non-functional
change.
ACKs for top commit:
practicalswift:
ACK 71f183a49b
laanwj:
ACK 71f183a49b
Tree-SHA512: 2c1d8caacd86424b16a9d92e5df19e0bedb51ae111eecad7e3bfa46447bc88e5fff1f32dacf6c4a28257ebb3d87e79f80f074ce2c523ce08b1a0c0a67ab44204
Check for a flag to turn linker warnings into errors. When flags are passed to
linkers via the compiler driver using a -Wl,-foo flag, linker warnings may be
swallowed rather than bubbling up.
Co-authored-by: fanquake <fanquake@gmail.com>
Stop the build if a warning is emitted due to `-Wgnu` and
`--enable-werror` has been used. As usual - this would help notice such
a warning that is about to be introduced in new code.
This is a followup to
https://github.com/bitcoin/bitcoin/pull/18088
build: ensure we aren't using GNU extensions
Enable -Wconditional-uninitialized to warn on potentially uninitialized
reads.
Fix the sole such warning in Bitcoin Core in GetRdRand(): r1 would be
set to 0 on rdrand failure, so initializing it to 0 is a non-functional
change.
From "Intel 64 and IA-32 ArchitecturesSoftware Developer's Manual" [1],
page 1711: "CF=1 indicates that the data in the destination is valid.
Otherwise CF=0 and the data in the destination operand will be returned
as zeros for the specified width."
[1] https://software.intel.com/sites/default/files/managed/39/c5/325462-sdm-vol-1-2abcd-3abcd.pdf
c31cbe7cfe Add C++17 test to Travis (Pieter Wuille)
7829685e27 Add configure option for c++17 (Pieter Wuille)
0fbde488b2 Support conversion between Spans of compatible types (Pieter Wuille)
7cbfebbf3d Update ax_cxx_compile_stdcxx.m4 (Pieter Wuille)
Pull request description:
This adds a `--enable-c++17` option to the configure script, fixes the only C++17 incompatibility (with a commit taken from #18468), and adds a Travis test for it.
This is all off by default, and release builds remain C++11.
It implements the first step of the plan in https://github.com/bitcoin/bitcoin/issues/16684.
ACKs for top commit:
elichai:
tACK c31cbe7cfe
practicalswift:
Tested ACK c31cbe7cfe
hebasto:
ACK c31cbe7cfe, tested on Linux Mint 19.3 both C++11 and C++17 modes. Compiled and passed tests locally.
Tree-SHA512: a4b00776dbceef9c12abbb404c6bcd48f7916ce24c8c7a14116355f64e817578b7fcddbedd5ce435322319d1e4de43429b68553f4d96d970c308fe3e3e59b9d1
182dbdf0f4 util: Detect posix_fallocate() instead of assuming (Vasil Dimov)
Pull request description:
Don't assume that `posix_fallocate()` is available on Linux and not
available on other operating systems. At least FreeBSD has it and we
are not using it.
Properly check whether `posix_fallocate()` is present and use it if it
is.
ACKs for top commit:
laanwj:
ACK 182dbdf0f4
Tree-SHA512: f9ed4bd661f33ff6b2b1150591e860b3c1f44e12b87c35e870d06a7013c4e841ed2bf17b41ad6b18fe471b0b23a4b5e42cf1400637180888e0bc56c254fe0766
b155fcda51 doc: fix typo in configure.ac (fanquake)
20a30922fb doc: note why we can't use thread_local with glibc back compat (fanquake)
Pull request description:
Given that we went through a [gitian build](https://github.com/bitcoin/bitcoin/pull/18681) to remember why this is the case, we might as well make a note of it in configure.ac.
[From #18681](https://github.com/bitcoin/bitcoin/pull/18681#issuecomment-615526634):
Looking at the Linux build log, this has failed with:
```bash
Checking glibc back compat...
bitcoind: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
bitcoind: failed IMPORTED_SYMBOLS
bitcoin-cli: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
bitcoin-cli: failed IMPORTED_SYMBOLS
bitcoin-tx: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
bitcoin-tx: failed IMPORTED_SYMBOLS
bitcoin-wallet: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
bitcoin-wallet: failed IMPORTED_SYMBOLS
test/test_bitcoin: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
test/test_bitcoin: failed IMPORTED_SYMBOLS
bench/bench_bitcoin: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
bench/bench_bitcoin: failed IMPORTED_SYMBOLS
qt/bitcoin-qt: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
```
`__cxa_thread_atexit_impl` is used for [thread_local variable destruction](https://sourceware.org/glibc/wiki/Destructor%20support%20for%20thread_local%20variables):
> To implement this support, glibc defines __cxa_thread_atexit_impl exclusively for use by libstdc++ (which has the __cxa_thread_atexit to wrap around it), that registers destructors for thread_local variables in a list. Upon thread or process exit, the destructors are called in reverse order in which they were added.
As suggested, this only became available in glibc 2.18. From the [2.18 release notes](https://sourceware.org/legacy-ml/libc-alpha/2013-08/msg00160.html):
> * Add support for calling C++11 thread_local object destructors on thread
and program exit. This needs compiler support for offloading C++11
destructor calls to glibc.
ACKs for top commit:
hebasto:
ACK b155fcda51
Tree-SHA512: 5b9567e4a70598a4b0b91956f44ae0d93091db17c84cbf9817dac6cfa992c97d3438a8b1bb66644c74891f2149e44984daed445d22de93ca8858c5b0eabefb40
Don't assume that `posix_fallocate()` is available on Linux and not
available on other operating systems. At least FreeBSD has it and we
are not using it.
Properly check whether `posix_fallocate()` is present and use it if it
is.
This reverts the changes made in merge commit
1b307613604883daea4913a65da30ae073c9dc4d:
This reverts commit b919efadff.
This reverts commit d54f64c6c7.
This reverts commit 787f40668d.
This reverts commit d630646662.
This reverts commit e6e44eedd5.
b919efadff depends: Use default macos clang compiler (Russell Yanofsky)
d54f64c6c7 Add multiprocess travis configuration (Russell Yanofsky)
787f40668d Set LD_LIBRARY_PATH consistently in travis tests (Russell Yanofsky)
d630646662 libmultiprocess depends build (Russell Yanofsky)
e6e44eedd5 Multiprocess build changes (Russell Yanofsky)
Pull request description:
This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/projects/10).
This splits autotools, depends build, and travis changes out of #10102, so code changes and build system changes can be reviewed separately.
ACKs for top commit:
hebasto:
re-ACK b919efadff, rebased only since my [previous](https://github.com/bitcoin/bitcoin/pull/16367#issuecomment-605514556) review.
Tree-SHA512: ebc5e403cc99a0d9629ed7fe1595e01d57e6d1255cbf03968a3196ff6f528f734c78060fdc065724ee1f923bcc5aa2b29470fcb36a7f15957eb57c76d58178a4
01a3392b1b Drop bitcoin-wallet dependency on libevent (Russell Yanofsky)
0660119ac3 Drop unintended bitcoin-tx dependency on libevent (Russell Yanofsky)
Pull request description:
This fixes compile errors trying to build bitcoin-tx and bitcoin-wallet without libevent, which were reported by Luke Dashjr in https://github.com/bitcoin/bitcoin/issues/18465
The fix avoiding `bitcoin-tx` dependency on libevent just adds a conditional build rule. This is implemented in the first commit (more details in commit description).
The fix avoiding `bitcoin-wallet` dependency on libevent requires minor code changes, because `bitcoin-wallet` (unlike `bitcoin-tx`) links against code that calls `urlDecode` / `evhttp_uridecode`. This fix is implemented in the second commit (again details in the commit description).
ACKs for top commit:
jonasschnelli:
utACK 01a3392b1b.
Tree-SHA512: d2245e912ab494cccceeb427a1eca8e55b01a0006ff93eebcfb5461ae7cecd1083ac2de443d9db036b18bdc6f0fb615546caaa20c585046f66d234937f74870a
Now that 0.20 branch has been split off, master is 0.20.99 (pre-0.21).
Also clean out release notes.
Tree-SHA512: bba6133ae9708f75206c8934901b9f9909a233330f4dfefb3c24175bf8e11631cdc89a5d24a22421a73083f7eb743e977db8020b87dfbd3c1e6043929a19a285
This was added in 386efb7695 to
address spammy Clang warnings when building with ccache.
The issue was addressed in ccache 3.2
(https://bugzilla.samba.org/show_bug.cgi?id=8118, Nov 2014),
and from a look at all major distros, it's only Debian Jessie
that has a version of ccache older than that (3.1).
Therefore I think it's acceptable to drop this workaround, and
re-enable warnings for unused driver arguments (when compiling
using Clang).
autotools and automake changes to support multiprocess execution.
This adds a new --enable-multiprocess flag, and build configuration code to
detect libraries needed for multiprocess support. The --enable-multiprocess
flag builds new bitcoin-node and bitcoin-gui executables, which are updated in
https://github.com/bitcoin/bitcoin/pull/10102 to communicate across processes.
But for now they are functionally equivalent to existing bitcoind and
bitcoin-qt executables.
Don't include util/url.cpp to libbitcoin_util.a when libevent isn't available.
This fixes a compile error trying to build bitcoin-tx without libevent reported
by Luke Dashjr in https://github.com/bitcoin/bitcoin/issues/18465Fixes#18465
faf7d4fa86 build: Add cov_fuzz target (MarcoFalke)
fac71e364e build: link fuzz/test_runner.py for out-of-tree builds (MarcoFalke)
faf2c5aca0 build: Remove unused USE_COVERAGE (MarcoFalke)
Pull request description:
Only libFuzzer is supported right now, so clang is required. Thus, this needs a workaround such as https://github.com/bitcoin/bitcoin/issues/12602#issuecomment-562788247
Can be tested with:
```
mkdir build && cd build
../configure --enable-fuzz --with-sanitizers=fuzzer --enable-lcov --enable-lcov-branch-coverage CC=clang CXX=clang++
make $MAKEJOBS
make cov_fuzz
ACKs for top commit:
practicalswift:
ACK faf7d4fa86
Tree-SHA512: 6828f8f81d95f6781713d0b09d7eba2ffdb50217e09ca839db61791a4ed70024859c7a0cb01d9eede79166d574dd57ece01f9d9fe2610d4a72a4ca4a4ce0b838
sysctl() on *BSD takes a "const int *name", whereas sysctl() on macOS
it takes an "int *name". So our configure check and sysctl() detection on
macOS currently fails:
```bash
/usr/include/sys/sysctl.h:759:9: note: candidate function not viable:
no known conversion from 'const int [2]' to 'int *' for 1st argument
int sysctl(int *, u_int, void *, size_t *, void *, size_t);
```
This change removes the name argument from the sysctl() detection check,
meaning we will detect correctly on macOS and *BSD.
For consistency we also switch to using the more generic, non-const
version of the name parameter in the rest of our usage.
This change adds to the BITCOIN_QT_CONFIGURE script ability to use
pkg-config for MinGW. All of the non-pkg-config paths are removed as
needless.
If depends is built with DEBUG=1 the configure script fails to pickup
Qt:
- for macOS host (similar, but not the same as issue 16391)
- for Windows host (regression)
fae86c38bc util: Remove unused MilliSleep (MarcoFalke)
fa9af06d91 scripted-diff: Replace MilliSleep with UninterruptibleSleep (MarcoFalke)
fa4620be78 util: Add UnintrruptibleSleep (MarcoFalke)
Pull request description:
We don't use the interruptible feature of boost's sleep anywhere, so replace it with the sleep in `std::thread`
ACKs for top commit:
ajtowns:
ACK fae86c38bc quick code review
practicalswift:
ACK fae86c38bc -- patch looks correct
sipa:
Concept and code review ACK fae86c38bc
fanquake:
ACK fae86c38bc - note that an instance of `DHAVE_WORKING_BOOST_SLEEP_FOR` was missed in the [linter](https://github.com/bitcoin/bitcoin/blob/master/test/lint/extended-lint-cppcheck.sh#L69), but that can be cleaned up later.
Tree-SHA512: 7c0f8eb197664b9f7d9fe6c472c77d384f11c797c913afc31de4b532e3b4fd9ea6dd174f92062ff9d1ec39b25e0900ca7c597435add87f0f2477d9557204848c
d76894987d logging: enable thread_local usage on macOS (fanquake)
Pull request description:
Now that we're building against a newer SDK (`10.14`), we should be able to enable `thread_local` usage on macOS. Have tested building and running locally, as well as cross-compiling and running the binaries on a macOS 10.14 system.
#### master 8a56f79d49
```bash
src/bitcoind -logthreadnames=1
2020-02-06T04:38:33Z [] Bitcoin Core version v0.19.99.0-8a56f79d4 (release build)
2020-02-06T04:38:33Z [] Assuming ancestors of block 00000000000000000005f8920febd3925f8272a6a71237563d78c2edfdd09ddf have valid signatures.
2020-02-06T04:38:33Z [] Setting nMinimumChainWork=000000000000000000000000000000000000000008ea3cf107ae0dec57f03fe8
2020-02-06T04:38:33Z [] Using the 'sse4(1way),sse41(4way),avx2(8way)' SHA256 implementation
2020-02-06T04:38:33Z [] Using RdSeed as additional entropy source
```
#### this PR d76894987d
```bash
checking for thread_local support... yes
...
src/bitcoind -logthreadnames=1
2020-02-06T04:17:49Z [net] net thread start
2020-02-06T04:17:49Z [opencon] opencon thread start
2020-02-06T04:17:49Z [dnsseed] dnsseed thread start
2020-02-06T04:17:49Z [init] init message: Done loading
2020-02-06T04:17:49Z [msghand] msghand thread start
2020-02-06T04:17:49Z [addcon] addcon thread start
...
2020-02-06T04:17:54Z [init] tor: Thread interrupt
2020-02-06T04:17:54Z [init] Shutdown: In progress...
```
From the [Xcode 8 release notes](https://developer.apple.com/library/archive/releasenotes/DeveloperTools/RN-Xcode/Chapters/Introduction.html#//apple_ref/doc/uid/TP40001051-CH1-SW78)
> C++ now supports the thread_local keyword, which declares thread-local storage (TLS) and supports C++ classes with non-trivial constructors and destructors. (9001553)
ACKs for top commit:
jonasschnelli:
Tested ACK d76894987d
nijynot:
ACK d768949
hebasto:
ACK d76894987d
Tree-SHA512: 48f3e4104b80bd7b6aedcef10bb1957b073530130f33af7c5cb59e876ac3f5480e53d7af1c0b226d809fe9eef1add3d6c3fb6de4af174966202c6030060ea823
677fb8e923 test: Add ubsan surpression for crc32c (Wladimir J. van der Laan)
8e68bb1dde build: Disable msvc warning 4722 for leveldb build (Aaron Clauson)
be23949765 build: MSVC changes for leveldb update (Aaron Clauson)
9ebdf04757 build: CRC32C build system integration (Wladimir J. van der Laan)
402252a808 build: Add LCOV exception for crc32c (Wladimir J. van der Laan)
3a037d0067 test: Add crc32c exception to various linters and generation scripts (Wladimir J. van der Laan)
84ff1b2076 test: Add crc32c to subtree check linter (Wladimir J. van der Laan)
7cf13a5134 doc: Add crc32c subtree to developer notes (Wladimir J. van der Laan)
24d02a9ac0 build: Update build system for new leveldb (Wladimir J. van der Laan)
2e1819311a Squashed 'src/crc32c/' content from commit 224988680f7673cd7c769963d4035cb315aa3388 (Wladimir J. van der Laan)
66480821b3 Squashed 'src/leveldb/' changes from f545dfabff4c2e9836efed094dba99a34fbc6b88..f8ae182c1e5176d12e816fb2217ae33a5472fdd7 (Wladimir J. van der Laan)
Pull request description:
This updates leveldb to currently newest upstream commit 0c40829872:
- CRC32C hardware acceleration is now an external library [crc32c](https://github.com/google/crc32c). This adds acceleration on ARM, and should be faster on x86 because of using prefetch. It also makes it easy to support similar instruction sets on other platforms in the future.
- Thread handling uses C++11, instead of platform specific code.
- Native windows environment was added. No need to maintain our own hacky one, anymore.
- Upstream now builds using CMake. This doesn't mean we need to use that (phew), but internal configuration changed to a a series of checks, instead of OS profiles. This means the blanket error "Cannot build leveldb for $host. Please file a bug report' is removed.
All changes: a53934a3ae...0c40829872
Pretty much all our changes have been subsumed by upstream, so we figured it was cleaner to start over with a new branch from upstream with the still-relevant patches applied: https://github.com/bitcoin-core/leveldb/tree/bitcoin-fork-new
There's quite some testing to be done (see below). See https://github.com/bitcoin-core/leveldb/issues/25 and https://github.com/bitcoin-core/leveldb/pull/26 for more history and context.
TODO:
- [x] Subtree `crc32c`
- [x] Make linters happy about crc32 subtree
- [x] Integrate `crc32c` library into build system
- [x] MSVC build system
ACKs for top commit:
sipa:
ACK 677fb8e923
Tree-SHA512: 37ee92a750e053e924bc4626b12bb3fd81faa9f8c5ebaa343931fee810c45ba05aa6051fdea82535fa351bf2be7297801b98af9469865fc5ead771650a5d6240
This flag was used when building 32-bit Windows executables, which we no-longer
do, and is not accepted by the linker for any of the hosts we currently build
for. i.e:
```bash
checking whether the linker accepts -Wl,--large-address-aware... no
```
--large-address-aware
If given, the appropriate bit in the "Characteristics" field of the COFF
header is set to indicate that this executable supports virtual addresses
greater than 2 gigabytes. This should be used in conjunction with the /3GB
or /USERVA=value megabytes switch in the "[operating systems]" section of
the BOOT .INI. Otherwise, this bit has no effect. [This option is specific
to PE targeted ports of the linker]
You can check that the appropriate bit in the COFF header of our current
Windows binaries is still be set using dumpbin. i.e:
```powershell
dumpbin /headers .\bitcoind.exe
FILE HEADER VALUES
<snip>
26 characteristics
Executable
Line numbers stripped
Application can handle large (>2GB) addresses
```
f7453dcc03 build: remove linking librt for backwards compatibility (fanquake)
Pull request description:
Now that we require glibc 2.17+, see #17538, we can remove linking librt
for backwards compatibility purposes. The `clock_*` functions from librt
were merged into glibc as part of the [2.17 release](https://sourceware.org/ml/libc-announce/2012/msg00001.html):
* The `clock_*` suite of functions (declared in <time.h>) is now available
directly in the main C library. Previously it was necessary to link with
-lrt to use these functions. This change has the effect that a
single-threaded program that uses a function such as `clock_gettime' (and
is not linked with -lrt) will no longer implicitly load the pthreads
library at runtime and so will not suffer the overheads associated with
multi-thread support in other code such as the C++ runtime library.
Note that `librt` is already unused by the RISC-V and AARCH64 binaries as their librts don't export any `clock_*` functions. As an example, you can find a diff of the arm32 vs arm64 librt symbols [here](https://gist.github.com/fanquake/b08cb1f0d14df3133395d7796ebf030c).
Below is the library usage for the `v0.19.0.1` release (can delete these tables pre-merge).
#### RISC-V
```bash
riscv/bin/bitcoin-cli: ['libpthread.so.0', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-riscv64-lp64d.so.1']
riscv/bin/bitcoin-qt: ['libpthread.so.0', 'libfontconfig.so.1', 'libfreetype.so.6', 'libxcb.so.1', 'libdl.so.2', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-riscv64-lp64d.so.1', 'libatomic.so.1']
riscv/bin/bitcoin-wallet: ['libpthread.so.0', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-riscv64-lp64d.so.1', 'libatomic.so.1']
riscv/bin/bitcoind: ['libpthread.so.0', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-riscv64-lp64d.so.1', 'libatomic.so.1']
riscv/bin/bitcoin-tx: ['libpthread.so.0', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-riscv64-lp64d.so.1']
riscv/bin/test_bitcoin: ['libpthread.so.0', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-riscv64-lp64d.so.1', 'libatomic.so.1']
```
#### AARCH64
```bash
aarch64/bin/bitcoin-cli: ['libpthread.so.0', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-aarch64.so.1']
aarch64/bin/bitcoin-qt: ['libpthread.so.0', 'libfontconfig.so.1', 'libfreetype.so.6', 'libxcb.so.1', 'libdl.so.2', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-aarch64.so.1']
aarch64/bin/bitcoin-wallet: ['libpthread.so.0', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-aarch64.so.1']
aarch64/bin/bitcoind: ['libpthread.so.0', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-aarch64.so.1']
aarch64/bin/bitcoin-tx: ['libpthread.so.0', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-aarch64.so.1']
aarch64/bin/test_bitcoin: ['libpthread.so.0', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-aarch64.so.1']
```
#### ARM LINUX GNUEABIHF
```bash
arm32/bin/bitcoin-cli: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-armhf.so.3']
arm32/bin/bitcoin-qt: ['libpthread.so.0', 'librt.so.1', 'libfontconfig.so.1', 'libfreetype.so.6', 'libxcb.so.1', 'libdl.so.2', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-armhf.so.3']
arm32/bin/bitcoin-wallet: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-armhf.so.3']
arm32/bin/bitcoind: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-armhf.so.3']
arm32/bin/bitcoin-tx: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-armhf.so.3']
arm32/bin/test_bitcoin: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-armhf.so.3']
```
#### LINUX X86_64
```bash
x86_64/bin/bitcoin-cli: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-x86-64.so.2']
x86_64/bin/bitcoin-qt: ['libpthread.so.0', 'librt.so.1', 'libfontconfig.so.1', 'libfreetype.so.6', 'libxcb.so.1', 'libdl.so.2', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-x86-64.so.2']
x86_64/bin/bitcoin-wallet: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-x86-64.so.2']
x86_64/bin/bitcoind: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-x86-64.so.2']
x86_64/bin/bitcoin-tx: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-x86-64.so.2']
x86_64/bin/test_bitcoin: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux-x86-64.so.2']
```
#### LINUX i686
```bash
i686/bin/bitcoin-cli: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux.so.2']
i686/bin/bitcoin-qt: ['libpthread.so.0', 'librt.so.1', 'libfontconfig.so.1', 'libfreetype.so.6', 'libxcb.so.1', 'libdl.so.2', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux.so.2']
i686/bin/bitcoin-wallet: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux.so.2']
i686/bin/bitcoind: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux.so.2']
i686/bin/bitcoin-tx: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux.so.2']
i686/bin/test_bitcoin: ['libpthread.so.0', 'librt.so.1', 'libm.so.6', 'libgcc_s.so.1', 'libc.so.6', 'ld-linux.so.2']
```
ACKs for top commit:
laanwj:
ACK f7453dcc03
Tree-SHA512: b418260edcda88583abfa386a592ebfb977d111e8e2ba887a30bf830b0b10dba429b9cfd615fad453ff0bb824225914ccb91433064b158ae1fbb9d20fc0b9937
Now that we require glibc 2.17+, #17538, we can remove linking in librt
for backwards compatibility purposes. The clock_* functions from librt
were merged into glibc as part of the 2.17 release.
* The `clock_*' suite of functions (declared in <time.h>) is now available
directly in the main C library. Previously it was necessary to link with
-lrt to use these functions. This change has the effect that a
single-threaded program that uses a function such as `clock_gettime' (and
is not linked with -lrt) will no longer implicitly load the pthreads
library at runtime and so will not suffer the overheads associated with
multi-thread support in other code such as the C++ runtime library.
https://sourceware.org/ml/libc-announce/2012/msg00001.html
Note that librt is already not linked by the RISC-V and AARCH64 binaries.
fanquake