configure.ac: Detect mallinfo automatically

Previously, configure.ac only checked whether glibc was available,
but other C runtime libraries like Newlib have mallinfo too.

This is a first step to remove configuration option --enable-malloc-logging
and replace it with a debug level configurable at runtime.

Change-Id: If30fc98a84158459e222fddf08043f46d6fa4112
Signed-off-by: R. Diez <rdiez-2006@rd10.de>
Reviewed-on: https://review.openocd.org/c/openocd/+/9394
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins

src/helper/log.c

@@ -25,23 +25,7 @@
 #include <stdarg.h>
 
 #ifdef _DEBUG_FREE_SPACE_
-#ifdef HAVE_MALLOC_H
-#include <malloc.h>
-#else
-#error "malloc.h is required to use --enable-malloc-logging"
-#endif
-
-#ifdef __GLIBC__
-#if __GLIBC_PREREQ(2, 33)
-#define FORDBLKS_FORMAT " %zu"
-#else
-/* glibc older than 2.33 (2021-02-01) use mallinfo(). Overwrite it */
-#define mallinfo2 mallinfo
-#define FORDBLKS_FORMAT " %d"
-#endif
-#else
-#error "GNU glibc is required to use --enable-malloc-logging"
-#endif
+#include <malloc.h>  // For mallinfo/mallinfo2.
 #endif
 
 int debug_level = LOG_LVL_INFO;
@@ -118,11 +102,23 @@ static void log_puts(enum log_levels level,
 		/* print with count and time information */
 		int64_t t = timeval_ms() - start;
 #ifdef _DEBUG_FREE_SPACE_
+#ifdef HAVE_MALLINFO2
 		struct mallinfo2 info = mallinfo2();
+#elif defined(HAVE_MALLINFO)
+		struct mallinfo info = mallinfo();
+#else
+#error "Configuration error: Neither mallinfo() nor mallinfo2() are available."
+#endif
 #endif
 		fprintf(log_output, "%s%d %" PRId64 " %s:%d %s()"
 #ifdef _DEBUG_FREE_SPACE_
-			FORDBLKS_FORMAT
+#ifdef HAVE_MALLINFO2
+			" %zu"
+#elif defined(HAVE_MALLINFO)
+			" %d"
+#else
+#error "Configuration error: Neither mallinfo() nor mallinfo2() are available."
+#endif
 #endif
 			": %s", log_strings[level + 1], count, t, file, line, function,
 #ifdef _DEBUG_FREE_SPACE_