[glib: 1/3] glib: ensure consistent abort-on-OOM with g_vasprintf & its callers

[Philip Withnall <pwithnall src gnome org>]

commit 14035010dd760d2202d03eba3ca392a488ff04eb
Author: Daniel P. Berrangé <berrange redhat com>
Date:   Fri Oct 4 13:52:39 2019 +0100

    glib: ensure consistent abort-on-OOM with g_vasprintf & its callers
    
    The g_vasprintf method is called by g_strdup_vprintf, g_strdup_printf,
    g_string_append_vprintf and more. It has three different implementations
    depending on what the build target platform supports:
    
      1. The gnulib impl appears to use the system malloc, but a
         '#define malloc g_malloc' causes it to use GLib's wrapper
         and thus abort on OOM. This mostly gets used on Windows
         platforms or UNIX platforms with broken printf formatting.
    
      2. The main impl mostly used on modern Linux/UNIX calls the
         system vasprintf which uses the system malloc and does not
         abort on OOM.
    
      3. The final impl used on remaining platforms calls system
         vsprintf on a buffer allocated by g_new, and thus always
         aborts on OOM.
    
    Of note is that impl 2 (using vasprintf) historically could abort on
    OOM, if the application had installed a non-system malloc impl with
    GLib. This was because the code would g_strndup the result from
    vasprintf() in that scenario. This was removed in:
    
      commit a3660532535f92cfac136435579ed4f23231f48c
      Author: Dan Winship <danw gnome org>
      Date:   Fri Aug 7 09:46:49 2015 -0400
    
        glib: remove deprecated g_mem_is_system_malloc() check in gprintf.c
    
    Having inconsistent OOM behaviour for the three impls is undesirable and
    aborting on OOM is normal pratice for GLib APIs. Thus we must thus ensure
    this happens in all impls of g_vasprintf.
    
    Fixes #1622
    
    Signed-off-by: Daniel P. Berrangé <berrange redhat com>

 glib/gprintf.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)
---
diff --git a/glib/gprintf.c b/glib/gprintf.c
index fc0a02a3b..d4d0b3e0c 100644
--- a/glib/gprintf.c
+++ b/glib/gprintf.c
@@ -20,6 +20,7 @@
 #include <stdarg.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <errno.h>
 
 #include "gprintf.h"
 #include "gprintfint.h"
@@ -327,9 +328,18 @@ g_vasprintf (gchar      **string,
 
 #elif defined (HAVE_VASPRINTF)
 
-  len = vasprintf (string, format, args);
-  if (len < 0)
-    *string = NULL;
+  {
+    int saved_errno;
+    len = vasprintf (string, format, args);
+    saved_errno = errno;
+    if (len < 0)
+      {
+        if (saved_errno == ENOMEM)
+          g_error ("%s: failed to allocate memory", G_STRLOC);
+        else
+          *string = NULL;
+      }
+  }
 
 #else