From 78e9e3f945935c91d8dfe0e832a95d6ea8d05f34 Mon Sep 17 00:00:00 2001
From: Richard Levitte <levitte@openssl.org>
Date: Sat, 18 Nov 2017 17:54:57 +0100
Subject: [PATCH] Configure: use a better method to identify gcc and derivates

Looking for 'gcc' and 'clang' in the output from the C compiler is
uncertain.  Some versions report argv[0], which might be /usr/bin/cc
(for example), and others might mention gcc without being gcc or a
derivate.

Better then to fetch predefined macros and checking if __GNUC__ and
__clang__ are defined.

Reviewed-by: Andy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4755)
---
 Configure | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/Configure b/Configure
index 60386d3959..a77ff0bac9 100755
--- a/Configure
+++ b/Configure
@@ -1269,7 +1269,7 @@ my ($prelflags,$postlflags)=split('%',$lflags);
 if (defined($postlflags))	{ $lflags=$postlflags;	}
 else				{ $lflags=$prelflags; undef $prelflags;	}
 
-if ($target =~ /^mingw/ && `$cc --target-help 2>&1` !~ m/\-mno\-cygwin/m)
+if ($target =~ /^mingw/ && `$cross_compile_prefix$cc --target-help 2>&1` !~ m/\-mno\-cygwin/m)
 	{
 	$cflags =~ s/\-mno\-cygwin\s*//;
 	$shared_ldflag =~ s/\-mno\-cygwin\s*//;
@@ -1661,18 +1661,25 @@ if ($shlib_version_number =~ /(^[0-9]*)\.([0-9\.]*)/)
 	$shlib_minor=$2;
 	}
 
-my $ecc = $cc;
-$ecc = "clang" if `$cc --version 2>&1` =~ /clang/;
+my %predefined;
+
+# collect compiler pre-defines from gcc or gcc-alike...
+open(PIPE, "$cross_compile_prefix$cc -dM -E -x c /dev/null 2>&1 |");
+while (<PIPE>) {
+  m/^#define\s+(\w+(?:\(\w+\))?)(?:\s+(.+))?/ or last;
+  $predefined{$1} = defined($2) ? $2 : "";
+}
+close(PIPE);
 
 if ($strict_warnings)
 	{
 	my $wopt;
-	die "ERROR --strict-warnings requires gcc or clang" unless ($ecc =~ /gcc$/ or $ecc =~ /clang$/);
+	die "ERROR --strict-warnings requires gcc or clang" unless defined($predefined{__GNUC__});
 	foreach $wopt (split /\s+/, $gcc_devteam_warn)
 		{
 		$cflags .= " $wopt" unless ($cflags =~ /(^|\s)$wopt(\s|$)/)
 		}
-	if ($ecc eq "clang")
+	if (defined($predefined{__clang__}))
 		{
 		foreach $wopt (split /\s+/, $clang_devteam_warn)
 			{
@@ -1723,15 +1730,14 @@ while (<IN>)
 		s/^NM=\s*/NM= \$\(CROSS_COMPILE\)/;
 		s/^RANLIB=\s*/RANLIB= \$\(CROSS_COMPILE\)/;
 		s/^RC=\s*/RC= \$\(CROSS_COMPILE\)/;
-		s/^MAKEDEPPROG=.*$/MAKEDEPPROG= \$\(CROSS_COMPILE\)$cc/ if $cc eq "gcc";
+		s/^MAKEDEPPROG=.*$/MAKEDEPPROG= \$\(CROSS_COMPILE\)$cc/ if $predefined{__GNUC__} >= 3;
 		}
 	else	{
 		s/^CC=.*$/CC= $cc/;
 		s/^AR=\s*ar/AR= $ar/;
 		s/^RANLIB=.*/RANLIB= $ranlib/;
 		s/^RC=.*/RC= $windres/;
-		s/^MAKEDEPPROG=.*$/MAKEDEPPROG= $cc/ if $cc eq "gcc";
-		s/^MAKEDEPPROG=.*$/MAKEDEPPROG= $cc/ if $ecc eq "gcc" || $ecc eq "clang";
+		s/^MAKEDEPPROG=.*$/MAKEDEPPROG= $cc/ if $predefined{__GNUC__} >= 3;
 		}
 	s/^CFLAG=.*$/CFLAG= $cflags/;
 	s/^DEPFLAG=.*$/DEPFLAG=$depflags/;
-- 
2.40.0