From fd5654cab1e5d317119f747abd245c620e8ba29b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pavel=20Jan=C3=ADk?= <Pavel@Janik.cz>
Date: Thu, 22 Sep 2016 16:36:03 +0200
Subject: [PATCH 1/2] Check and enable -Wshadow by default.

---
 configure.ac | 1 +
 1 file changed, 1 insertion(+)

diff --git a/configure.ac b/configure.ac
index 25b828f18c6..c95489d4d72 100644
--- a/configure.ac
+++ b/configure.ac
@@ -203,6 +203,7 @@ if test "x$CXXFLAGS_overridden" = "xno"; then
   AX_CHECK_COMPILE_FLAG([-Wextra],[CXXFLAGS="$CXXFLAGS -Wextra"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wformat],[CXXFLAGS="$CXXFLAGS -Wformat"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wformat-security],[CXXFLAGS="$CXXFLAGS -Wformat-security"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wshadow],[CXXFLAGS="$CXXFLAGS -Wshadow"],,[[$CXXFLAG_WERROR]])
 
   ## Some compilers (gcc) ignore unknown -Wno-* options, but warn about all
   ## unknown options if any other warning is produced. Test the -Wfoo case, and

From 359bac7cff235f60c8f5abb66a861c5a7b9a2b6d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pavel=20Jan=C3=ADk?= <Pavel@Janik.cz>
Date: Thu, 22 Sep 2016 16:39:25 +0200
Subject: [PATCH 2/2] Add notes about variable names and shadowing

---
 doc/developer-notes.md | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/doc/developer-notes.md b/doc/developer-notes.md
index 70c0690ba3c..b0794e6d30c 100644
--- a/doc/developer-notes.md
+++ b/doc/developer-notes.md
@@ -331,6 +331,32 @@ Strings and formatting
 
   - *Rationale*: Bitcoin Core uses tinyformat, which is type safe. Leave them out to avoid confusion
 
+Variable names
+--------------
+
+The shadowing warning (`-Wshadow`) is enabled by default. It prevents issues rising
+from using a different variable with the same name.
+
+Please name variables so that their names do not shadow variables defined in the source code.
+
+E.g. in member initializers, prepend `_` to the argument name shadowing the
+member name:
+
+```c++
+class AddressBookPage
+{
+    Mode mode;
+}
+
+AddressBookPage::AddressBookPage(Mode _mode) :
+      mode(_mode)
+...
+```
+
+When using nested cycles, do not name the inner cycle variable the same as in
+upper cycle etc.
+
+
 Threads and synchronization
 ----------------------------