Make the use of mdebug backtrace a separate option

To force it on anyone using --strict-warnings was the wrong move, as
this is an option best left to those who know what they're doing.

Use with care!
Reviewed-by: NAndy Polyakov <appro@openssl.org>

Configure

@@ -109,9 +109,9 @@ my $clang_devteam_warn = ""
         . " -Wmissing-variable-declarations"
         ;
 
-# These are used in addition to $gcc_devteam_warn unless this is a mingw build.
-# This adds backtrace information to the memory leak info.
-my $memleak_devteam_backtrace = "-rdynamic -DCRYPTO_MDEBUG_BACKTRACE";
+# This adds backtrace information to the memory leak info.  Is only used
+# when crypto-mdebug-backtrace is enabled.
+my $memleak_devteam_backtrace = "-rdynamic";
 
 my $strict_warnings = 0;
 
@@ -252,6 +252,7 @@ my @disablables = (
     "cms",
     "comp",
     "crypto-mdebug",
+    "crypto-mdebug-backtrace",
     "ct",
     "deprecated",
     "des",
@@ -377,6 +378,8 @@ my @disable_cascades = (
 
     # SRP and HEARTBEATS require TLSEXT
     "tlsext"		=> [ "srp", "heartbeats" ],
+
+    "crypto-mdebug"     => [ "crypto-mdebug-backtrace" ],
     );
 
 # Avoid protocol support holes.  Also disable all versions below N, if version
@@ -1162,16 +1165,17 @@ if ($strict_warnings)
 			$config{cflags} .= " $wopt" unless ($config{cflags} =~ /(^|\s)$wopt(\s|$)/)
 			}
 		}
-	if ($target !~ /^mingw/)
+	}
+
+unless ($disabled{"crypto-mdebug-backtrace"})
+	{
+	foreach my $wopt (split /\s+/, $memleak_devteam_backtrace)
 		{
-		foreach $wopt (split /\s+/, $memleak_devteam_backtrace)
-			{
-			$config{cflags} .= " $wopt" unless ($config{cflags} =~ /(^|\s)$wopt(\s|$)/)
-			}
-		if ($target =~ /^BSD-/)
-			{
-			$config{ex_libs} .= " -lexecinfo";
-			}
+		$config{cflags} .= " $wopt" unless ($config{cflags} =~ /(^|\s)$wopt(\s|$)/)
+		}
+	if ($target =~ /^BSD-/)
+		{
+		$config{ex_libs} .= " -lexecinfo";
 		}
 	}
 

crypto/mem_dbg.c

@@ -116,7 +116,8 @@
 #include <openssl/buffer.h>
 #include <openssl/bio.h>
 #include <openssl/lhash.h>
-#if defined(CRYPTO_MDEBUG_BACKTRACE) && defined(__GNUC__)
+
+#ifndef OPENSSL_NO_CRYPTO_MDEBUG_BACKTRACE
 # include <execinfo.h>
 #endif
 
@@ -171,7 +172,7 @@ struct mem_st {
     unsigned long order;
     time_t time;
     APP_INFO *app_info;
-#if defined(CRYPTO_MDEBUG_BACKTRACE) && defined(__GNUC__)
+#ifndef OPENSSL_NO_CRYPTO_MDEBUG_BACKTRACE
     void *array[30];
     size_t array_siz;
 #endif
@@ -445,7 +446,7 @@ void CRYPTO_mem_debug_malloc(void *addr, size_t num, int before_p,
                 m->order = order;
             }
             m->order = order++;
-# if defined(CRYPTO_MDEBUG_BACKTRACE) && defined(__GNUC__)
+# ifndef OPENSSL_NO_CRYPTO_MDEBUG_BACKTRACE
             m->array_siz = backtrace(m->array, OSSL_NELEM(m->array));
 # endif
             m->time = time(NULL);
@@ -525,7 +526,7 @@ void CRYPTO_mem_debug_realloc(void *addr1, void *addr2, size_t num,
             if (mp != NULL) {
                 mp->addr = addr2;
                 mp->num = num;
-#if defined(CRYPTO_MDEBUG_BACKTRACE) && defined(__GNUC__)
+#ifndef OPENSSL_NO_CRYPTO_MDEBUG_BACKTRACE
                 mp->array_siz = backtrace(mp->array, OSSL_NELEM(mp->array));
 #endif
                 (void)lh_MEM_insert(mh, mp);
@@ -618,7 +619,7 @@ static void print_leak(const MEM *m, MEM_LEAK *l)
         while (amip && !CRYPTO_THREADID_cmp(&amip->threadid, &ti));
     }
 
-#if defined(CRYPTO_MDEBUG_BACKTRACE) && defined(__GNUC__)
+#ifndef OPENSSL_NO_CRYPTO_MDEBUG_BACKTRACE
     {
         size_t i;
         char **strings = backtrace_symbols(m->array, m->array_siz);