Re: [Qemu-devel] [PATCH 11/15] monitor error: Make printf()-like functions return a value

[Markus Armbruster]

Markus Armbruster <address@hidden> writes:

> printf() & friends return the number of characters written on success,
> negative value on error.
>
> monitor_printf(), monitor_vfprintf(), monitor_vprintf(),
> error_printf(), error_printf_unless_qmp(), error_vprintf(), and
> error_vprintf_unless_qmp() return void.  Some of them carry a TODO
> comment asking for int instead.
>
> Improve them to return int like printf() does.
>
> This makes our use of monitor_printf() as fprintf_function slightly
> less dirty: the function cast no longer adds a return value that isn't
> there.  It still changes a parameter's pointer type.  That will be
> addressed in a future commit.
>
> monitor_vfprintf() always returns zero.  Improve it to return the
> proper value.
>
> Cc: Dr. David Alan Gilbert <address@hidden>
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
[...]
> diff --git a/stubs/error-printf.c b/stubs/error-printf.c
> index 99c6406668..537298209d 100644
> --- a/stubs/error-printf.c
> +++ b/stubs/error-printf.c
> @@ -2,19 +2,19 @@
>  #include "qemu-common.h"
>  #include "qemu/error-report.h"
>  
> -void error_vprintf(const char *fmt, va_list ap)
> +int error_vprintf(const char *fmt, va_list ap)
>  {
>      if (g_test_initialized() && !g_test_subprocess() &&
>          getenv("QTEST_SILENT_ERRORS")) {
>          char *msg = g_strdup_vprintf(fmt, ap);
>          g_test_message("%s", msg);
>          g_free(msg);
> -    } else {
> -        vfprintf(stderr, fmt, ap);
> +        return strlen(msg);

Use after free.  Obvious fixup appended.

>      }
> +    return vfprintf(stderr, fmt, ap);
>  }
>  
> -void error_vprintf_unless_qmp(const char *fmt, va_list ap)
> +int error_vprintf_unless_qmp(const char *fmt, va_list ap)
>  {
> -    error_vprintf(fmt, ap);
> +    return error_vprintf(fmt, ap);
>  }
[...]

diff --git a/stubs/error-printf.c b/stubs/error-printf.c
index 537298209d..1f9d3b3714 100644
--- a/stubs/error-printf.c
+++ b/stubs/error-printf.c
@@ -4,12 +4,15 @@
 
 int error_vprintf(const char *fmt, va_list ap)
 {
+    int ret;
+
     if (g_test_initialized() && !g_test_subprocess() &&
         getenv("QTEST_SILENT_ERRORS")) {
         char *msg = g_strdup_vprintf(fmt, ap);
         g_test_message("%s", msg);
+        ret = strlen(msg);
         g_free(msg);
-        return strlen(msg);
+        return ret;
     }
     return vfprintf(stderr, fmt, ap);
 }