osdep: Work around MinGW assert

In several places we use assert(FEATURE), and assume that if FEATURE
is disabled, all following code is removed as unreachable.  Which allows
us to compile-out functions that are only present with FEATURE, and
have a link-time failure if the functions remain used.

MinGW does not mark its internal function _assert() as noreturn, so the
compiler cannot see when code is unreachable, which leads to link errors
for this host that are not present elsewhere.

The current build-time failure concerns 62823083b8a2, but I remember
having seen this same error before.  Fix it once and for all for MinGW.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20181022181623.8810-1-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 4f8559e550..3bf48bcdec 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -123,6 +123,18 @@ extern int daemon(int, int);
 #include "qemu/typedefs.h"
 
 /*
+ * For mingw, as of v6.0.0, the function implementing the assert macro is
+ * not marked as noreturn, so the compiler cannot delete code following an
+ * assert(false) as unused.  We rely on this within the code base to delete
+ * code that is unreachable when features are disabled.
+ * All supported versions of Glib's g_assert() satisfy this requirement.
+ */
+#ifdef __MINGW32__
+#undef assert
+#define assert(x)  g_assert(x)
+#endif
+
+/*
  * According to waitpid man page:
  * WCOREDUMP
  *  This  macro  is  not  specified  in POSIX.1-2001 and is not