From d5c0351055d5709da8f3e16c91348092fdb481aa Mon Sep 17 00:00:00 2001
From: Marcel Raad <Marcel.Raad@teamviewer.com>
Date: Mon, 9 Jul 2018 18:38:23 +0200
Subject: [PATCH] configure: conditionally enable pedantic-errors

Enable pedantic-errors for GCC >= 5 with --enable-werror. Before GCC 5,
pedantic-errors was synonymous to -Werror=pedantic [0], which is still
the case for clang [1]. With GCC 5, it became complementary [2].

Also fix a resulting error in acinclude.m4 as main's return type was
missing, which is illegal in C99.

[0] https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/Warning-Options.html
[1] https://clang.llvm.org/docs/UsersManual.html#options-to-control-error-and-warning-messages
[2] https://gcc.gnu.org/onlinedocs/gcc-5.1.0/gcc/Warning-Options.html

Closes https://github.com/curl/curl/pull/2747
---
 acinclude.m4 | 2 +-
 configure.ac | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/acinclude.m4 b/acinclude.m4
index f32e86cda..355ee3a61 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -2158,7 +2158,7 @@ AC_DEFUN([CURL_VERIFY_RUNTIMELIBS], [
     dnl point also is available run-time!
     AC_MSG_CHECKING([run-time libs availability])
     CURL_RUN_IFELSE([
-main()
+int main()
 {
   return 0;
 }
diff --git a/configure.ac b/configure.ac
index 18b7ae0f1..ff8f5df9b 100755
--- a/configure.ac
+++ b/configure.ac
@@ -61,6 +61,13 @@ AC_SUBST(CONFIGURE_OPTIONS)
 CURL_CFLAG_EXTRAS=""
 if test X"$want_werror" = Xyes; then
   CURL_CFLAG_EXTRAS="-Werror"
+  if test "$compiler_id" = "GNU_C"; then
+    dnl enable -pedantic-errors for GCC 5 and later,
+    dnl as before that it was the same as -Werror=pedantic
+    if test "$compiler_num" -ge "500"; then
+      CURL_CFLAG_EXTRAS="$CURL_CFLAG_EXTRAS -pedantic-errors"
+    fi
+  fi
 fi
 AC_SUBST(CURL_CFLAG_EXTRAS)