From 2699f446739bf3092c41099f9d1de692f0c21799 Mon Sep 17 00:00:00 2001
From: "Wladimir J. van der Laan" <laanwj@protonmail.com>
Date: Wed, 15 Jul 2020 13:51:02 +0200
Subject: [PATCH] Merge #18882: build: fix -Wformat-security check when
 compiling with GCC

6cef3652d143a1dddad1254cab0953561d24c1fa build: fix -Wformat-security check when compiling with GCC (fanquake)

Pull request description:

  GCC expects `-Wformat` to be passed with [`-Wformat-security`](https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html), which means
  when we test for it in configure 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
  ```

  and never gets added to our CXX flags. Note that Clang does not have this requirement and the check is working correctly there.

  The change in this PR is the simple fix, however we might want to consider using something like `-Wformat=2` in future, which in GCC is equivalent to `-Wformat -Wformat-nonliteral -Wformat-security -Wformat-y2k.` and similar [in Clang](https://clang.llvm.org/docs/DiagnosticsReference.html#wformat-2).

ACKs for top commit:
  practicalswift:
    ACK 6cef3652d143a1dddad1254cab0953561d24c1fa
  laanwj:
    ACK 6cef3652d143a1dddad1254cab0953561d24c1fa

Tree-SHA512: f9230d42af39f85ea9d2f55dbbebd2bae4740fe59b0da2e092af3ac9ef7e6799d3a4cf83eb64574c63982e5f6b14e226d44c84fa0335255d65c9947d86a1ea38
---
 configure.ac | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index 3750127ea4..017e2e00cd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -441,11 +441,11 @@ if test "x$CXXFLAGS_overridden" = "xno"; then
   AX_CHECK_COMPILE_FLAG([-Wall],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wall"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wextra],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wextra"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wgnu],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wgnu"],,[[$CXXFLAG_WERROR]])
-  AX_CHECK_COMPILE_FLAG([-Wformat],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wformat"],,[[$CXXFLAG_WERROR]])
+  dnl some compilers will ignore -Wformat-security without -Wformat, so just combine the two here.
+  AX_CHECK_COMPILE_FLAG([-Wformat -Wformat-security],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wformat -Wformat-security"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wvla],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wvla"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wshadow-field],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wshadow-field"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wswitch],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wswitch"],,[[$CXXFLAG_WERROR]])
-  AX_CHECK_COMPILE_FLAG([-Wformat-security],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wformat-security"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wthread-safety],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wthread-safety"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wrange-loop-analysis],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wrange-loop-analysis"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wredundant-decls],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wredundant-decls"],,[[$CXXFLAG_WERROR]])