[vlc-devel] [PATCH 5/5] win32: vlc_fix_format_string - various fixes

[davidf+nntp at woaf.net]

From: David Flynn <davidf at rd.bbc.co.uk>

- avoid mingw problems with %l*
- avoid using %I32 on Win32, since wince doesn't support it
- unify WIN64 and WIN32 cases.
- if malloc were to fail(!), don't allow unfiltered format string
  to get passed to *printf.
  (substitues an error message)

Signed-off-by: David Flynn <davidf at rd.bbc.co.uk>
---
 include/vlc_fixups.h |   94 +++++++++++++++++++++++++------------------------
 1 files changed, 48 insertions(+), 46 deletions(-)

diff --git a/include/vlc_fixups.h b/include/vlc_fixups.h
index 02cf88c..6088eb5 100644
--- a/include/vlc_fixups.h
+++ b/include/vlc_fixups.h
@@ -39,56 +39,58 @@ static inline char *strdup (const char *str)
 #endif
 
 #ifdef WIN32
-/* Windows' printf doesn't support %z modifiers, thus we need to rewrite
- * the format string in a wrapper. */
 # include <string.h>
 # include <stdlib.h>
-static inline char *vlc_fix_format_string (const char *format)
+/**
+ * vlc_fix_format_string:
+ * @format: address of format string to fix (format string is not modified)
+ *
+ * Windows' printf doesn't support %z size modifiers.
+ * Fix a *printf format string to make it safe for mingw/MSVCRT run times:
+ *  %z* (not supported in MSVCRT) -> either %I64* or %I32.
+ *
+ * Returns: 1 if *format must be free()d; 0 otherwise
+ */
+static inline int vlc_fix_format_string (const char **format)
 {
-    char *fmt;
-# ifdef WIN64
-    const char *src = format, *tmp;
-    char *dst;
-    size_t n = 0;
-    while ((tmp = strstr (src, "%z")) != NULL)
+    int n = 0;
+    const char *tmp = *format;
+    while ((tmp = strstr (tmp, "%z")) != NULL)
     {
         n++;
-        src = tmp + 2;
+        tmp += 2;
     }
-    if (n == 0)
-        return NULL;
+    if (!n)
+        return 0;
 
-    fmt = (char*)malloc (strlen (format) + n + 1);
-    if (fmt == NULL)
-        return NULL;
+    char *dst = (char*)malloc (strlen (*format) + 2*n + 1);
+    if (!dst)
+    {
+        *format = "vlc_fix_format_string: due to malloc failure, unable to fix unsafe string";
+        return 0;
+    }
 
-    src = format;
-    dst = fmt;
+    const char *src = *format;
+    *format = dst;
     while ((tmp = strstr (src, "%z")) != NULL)
     {
+        /* NB, don't use %l*, as this is buggy in mingw*/
         size_t d = tmp - src;
         memcpy (dst, src, d);
         dst += d;
-        memcpy (dst, "%ll", 3);
-        dst += 3;
+        *dst++ = '%';
+# ifdef WIN64
+        *dst++ = 'I';
+        *dst++ = '6';
+        *dst++ = '4';
+# else /* ie: WIN32 */
+        /* on win32, since the default size is 32bit, dont specify
+         * a modifer.  (I32 isn't on wince, l doesn't work on mingw) */
+# endif
         src = tmp + 2;
     }
     strcpy (dst, src);
-# else
-    char *f;
-    if (strstr (format, "%z") == NULL)
-        return NULL;
-
-    fmt = strdup (format);
-    if (fmt == NULL)
-        return NULL;
-
-    while ((f = strstr (fmt, "%z")) != NULL)
-    {
-       f[1] = 'l';
-    }
-# endif
-    return fmt;
+    return 1;
 }
 
 # include <stdio.h>
@@ -96,40 +98,40 @@ static inline char *vlc_fix_format_string (const char *format)
 
 static inline int vlc_vprintf (const char *format, va_list ap)
 {
-    char *fmt = vlc_fix_format_string (format);
-    int ret = vprintf (fmt ? fmt : format, ap);
-    free (fmt);
+    int must_free = vlc_fix_format_string (&format);
+    int ret = vprintf (format, ap);
+    if (must_free) free ((char *)format);
     return ret;
 }
 # define vprintf vlc_vprintf
 
 static inline int vlc_vfprintf (FILE *stream, const char *format, va_list ap)
 {
-    char *fmt = vlc_fix_format_string (format);
-    int ret = vfprintf (stream, fmt ? fmt : format, ap);
-    free (fmt);
+    int must_free = vlc_fix_format_string (&format);
+    int ret = vfprintf (stream, format, ap);
+    if (must_free) free ((char *)format);
     return ret;
 }
 # define vfprintf vlc_vfprintf
 
 static inline int vlc_vsprintf (char *str, const char *format, va_list ap)
 {
-    char *fmt = vlc_fix_format_string (format);
-    int ret = vsprintf (str, fmt ? fmt : format, ap);
-    free (fmt);
+    int must_free = vlc_fix_format_string (&format);
+    int ret = vsprintf (str, format, ap);
+    if (must_free) free ((char *)format);
     return ret;
 }
 # define vsprintf vlc_vsprintf
 
 static inline int vlc_vsnprintf (char *str, size_t size, const char *format, va_list ap)
 {
-    char *fmt = vlc_fix_format_string (format);
+    int must_free = vlc_fix_format_string (&format);
     /* traditionally, MSVCRT has provided vsnprintf as _vsnprintf;
      * to 'aid' portability/standards compliance, mingw provides a
      * static version of vsnprintf that is buggy.  Be sure to use
      * MSVCRT version, at least it behaves as expected */
-    int ret = _vsnprintf (str, size, fmt ? fmt : format, ap);
-    free (fmt);
+    int ret = _vsnprintf (str, size, format, ap);
+    if (must_free) free ((char *)format);
     return ret;
 }
 # define vsnprintf vlc_vsnprintf
-- 
1.5.6.5