[PATCH v3 09/10] clang: warn when the comma operator is used

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

When compiling Git using `clang`, the `-Wcomma` option can be used to
warn about code using the comma operator (because it is typically
unintentional and wants to use the semicolon instead).

Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 config.mak.dev | 4 ++++
 meson.build    | 1 +
 2 files changed, 5 insertions(+)

diff --git a/config.mak.dev b/config.mak.dev
index 0fd8cc4d355..31423638169 100644
--- a/config.mak.dev
+++ b/config.mak.dev
@@ -40,6 +40,10 @@ DEVELOPER_CFLAGS += -Wvla
 DEVELOPER_CFLAGS += -Wwrite-strings
 DEVELOPER_CFLAGS += -fno-common
 
+ifneq ($(filter clang9,$(COMPILER_FEATURES)),)
+DEVELOPER_CFLAGS += -Wcomma
+endif
+
 ifneq ($(filter clang4,$(COMPILER_FEATURES)),)
 DEVELOPER_CFLAGS += -Wtautological-constant-out-of-range-compare
 endif
diff --git a/meson.build b/meson.build
index efe2871c9db..fd8c05dec91 100644
--- a/meson.build
+++ b/meson.build
@@ -715,6 +715,7 @@ libgit_dependencies = [ ]
 # Makefile.
 if get_option('warning_level') in ['2','3', 'everything'] and compiler.get_argument_syntax() == 'gcc'
   foreach cflag : [
+    '-Wcomma',
     '-Wdeclaration-after-statement',
     '-Wformat-security',
     '-Wold-style-definition',
-- 
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