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)

diff --git a/Configure b/Configure
index 60386d3959875809915dbd899a9c48ca39a0d07f..a77ff0bac96f0efd47bad8fce19d87a6eeefb752 100755 (executable)
--- 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/;