From 3cd8506ff89aa9e7cc596d67b3ad09b2c41d658c Mon Sep 17 00:00:00 2001
From: Jean-Francois Dockes <jf@dockes.org>
Date: Tue, 17 Aug 2021 09:16:55 +0200
Subject: [PATCH] Use macro to detect real gcc as opposed to e.g. clang
 disguising as gcc

---
 src/common/conf_post.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/common/conf_post.h b/src/common/conf_post.h
index eac832c0..7093ead2 100644
--- a/src/common/conf_post.h
+++ b/src/common/conf_post.h
@@ -67,7 +67,14 @@ typedef int ssize_t;
 #  define PRETEND_USE(expr) ((void)(expr))
 #endif /* PRETEND_USE */
 
-#ifdef __GNUC__
+// It's complicated to really detect gnu gcc because other compilers define __GNUC__
+// See stackoverflow questions/38499462/how-to-tell-clang-to-stop-pretending-to-be-other-compilers
+#if defined(__GNUC__) && !defined(__llvm__) && !defined(__INTEL_COMPILER)
+#define REAL_GCC   __GNUC__ // probably
+#endif
+
+#ifdef REAL_GCC
+// Older gcc versions pretended to supply std::regex, but the resulting programs mostly crashed.
 #include <features.h>
 #if ! __GNUC_PREREQ(6,0)
 #define NO_STD_REGEX 1