From b6627956b63c603654d67bd349a8c6afac421131 Mon Sep 17 00:00:00 2001
From: Paulo Matos <pmatos@linki.tools>
Date: Tue, 12 Nov 2019 19:26:36 +0100
Subject: [PATCH] Improve gcc detection in configure script (#2897)

Improve gcc detection in configure script

We have been detecting gcc by the CC variable but this fails under
ubuntu for example where you might specify CC='gcc-8' to ./configure.
Also consider clang impersonator to be gcc.

Related to #2890
---
 racket/src/cfg-racket          |  8 +++++++-
 racket/src/racket/configure.ac | 10 +++++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/racket/src/cfg-racket b/racket/src/cfg-racket
index abd2b2710e..b3af235ef6 100755
--- a/racket/src/cfg-racket
+++ b/racket/src/cfg-racket
@@ -4610,7 +4610,13 @@ SUB_CONFIGURE_EXTRAS="${SUB_CONFIGURE_EXTRAS} AR_FLAGS="'"'"${ARFLAGS}"'"'
 is_gmake=`make -v no-such-target-we-hope 2>&1 | grep "GNU Make"`
 
 # If using gcc, we want all warnings:
-if test "$CC" = "gcc" ; then
+is_gcc=`$CC -v 2>&1 | tail -n 1 | grep -E '^gcc version [[:digit:]]+\.[[:digit:]]+\.[[:digit:]]+ \([^\)]+\)[[:space:]]*$'`
+
+# We also need to test if $CC is gcc itself because on mac,
+# where clang impersonates gcc, although is_gcc is false, we want
+# to use it as if it was gcc.
+# See https://github.com/racket/racket/pull/2897#pullrequestreview-314906673
+if test "$is_gcc" != "" || test "`basename $CC`" = "gcc"; then
   COMPFLAGS="$COMPFLAGS -Wall"
 
   # Use -MMD when we have gcc and gnumake:
diff --git a/racket/src/racket/configure.ac b/racket/src/racket/configure.ac
index c563aa4409..ed0c5bd171 100644
--- a/racket/src/racket/configure.ac
+++ b/racket/src/racket/configure.ac
@@ -463,7 +463,15 @@ SUB_CONFIGURE_EXTRAS="${SUB_CONFIGURE_EXTRAS} AR_FLAGS="'"'"${ARFLAGS}"'"'
 is_gmake=`make -v no-such-target-we-hope 2>&1 | grep "GNU Make"`
 
 # If using gcc, we want all warnings:
-if test "$CC" = "gcc" ; then 
+changequote(<<, >>)dnl
+is_gcc=`$CC -v 2>&1 | tail -n 1 | grep -E '^gcc version [[:digit:]]+\.[[:digit:]]+\.[[:digit:]]+ \([^\)]+\)[[:space:]]*$'`
+changequote([, ])dnl
+
+# We also need to test if $CC is gcc itself because on mac,
+# where clang impersonates gcc, although is_gcc is false, we want
+# to use it as if it was gcc.
+# See https://github.com/racket/racket/pull/2897#pullrequestreview-314906673
+if test "$is_gcc" != "" || test "`basename $CC`" = "gcc"; then
   COMPFLAGS="$COMPFLAGS -Wall"
 
   # Use -MMD when we have gcc and gnumake: