Re: [PATCH] tests/unit/test-io-channel-command: Silence GCC error "maybe-uninitialized"

[Alex Bennée]

Bernhard Beschow <shentey@gmail.com> writes:

> GCC issues a false positive warning, resulting in build failure with -Werror:
>
>   In file included from /usr/lib/glib-2.0/include/glibconfig.h:9,
>                    from /usr/include/glib-2.0/glib/gtypes.h:34,
>                    from /usr/include/glib-2.0/glib/galloca.h:34,
>                    from /usr/include/glib-2.0/glib.h:32,
>                    from ../src/include/glib-compat.h:32,
>                    from ../src/include/qemu/osdep.h:144,
>                    from ../src/tests/unit/test-io-channel-command.c:21:
>   /usr/include/glib-2.0/glib/gmacros.h: In function 
> ‘test_io_channel_command_fifo’:
>   /usr/include/glib-2.0/glib/gmacros.h:1333:105: error: ‘dstargv’ may be used 
> uninitialized [-Werror=maybe-uninitialized]
>    1333 |   static G_GNUC_UNUSED inline void _GLIB_AUTO_FUNC_NAME(TypeName) 
> (TypeName *_ptr) { if (*_ptr != none) (func) (*_ptr); }     \
>         |                                                                     
>                                     ^
>   ../src/tests/unit/test-io-channel-command.c:39:19: note: ‘dstargv’ was 
> declared here
>      39 |     g_auto(GStrv) dstargv;
>         |                   ^~~~~~~
>   /usr/include/glib-2.0/glib/gmacros.h:1333:105: error: ‘srcargv’ may
> be used uninitialized [-Werror=maybe-uninitialized]
>    1333 | static G_GNUC_UNUSED inline void
> _GLIB_AUTO_FUNC_NAME(TypeName) (TypeName *_ptr) { if (*_ptr != none)
> (func) (*_ptr); } \
>         |                                                                     
>                                     ^
>   ../src/tests/unit/test-io-channel-command.c:38:19: note: ‘srcargv’ was 
> declared here
>      38 |     g_auto(GStrv) srcargv;
>         |                   ^~~~~~~
>   cc1: all warnings being treated as errors
>
> GCC version:
>
>   $ gcc --version
>   gcc (GCC) 12.2.0
>
> Fixes: 68406d10859385c88da73d0106254a7f47e6652e ('tests/unit: cleanups for 
> test-io-channel-command')
> Signed-off-by: Bernhard Beschow <shentey@gmail.com>
> ---
>  tests/unit/test-io-channel-command.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tests/unit/test-io-channel-command.c 
> b/tests/unit/test-io-channel-command.c
> index 43e29c8cfb..ba0717d3c3 100644
> --- a/tests/unit/test-io-channel-command.c
> +++ b/tests/unit/test-io-channel-command.c
> @@ -35,8 +35,8 @@ static void test_io_channel_command_fifo(bool async)
>      g_autofree gchar *fifo = g_strdup_printf("%s/%s", tmpdir, TEST_FIFO);
>      g_autoptr(GString) srcargs = g_string_new(socat);
>      g_autoptr(GString) dstargs = g_string_new(socat);
> -    g_auto(GStrv) srcargv;
> -    g_auto(GStrv) dstargv;
> +    g_auto(GStrv) srcargv = NULL;
> +    g_auto(GStrv) dstargv = NULL;
>      QIOChannel *src, *dst;
>      QIOChannelTest *test;

Another approach would be to drop the GString usage which is premature
and then we can allocate everything in order:

--8<---------------cut here---------------start------------->8---
modified   tests/unit/test-io-channel-command.c
@@ -33,19 +33,13 @@ static void test_io_channel_command_fifo(bool async)
 {
     g_autofree gchar *tmpdir = g_dir_make_tmp("qemu-test-io-channel.XXXXXX", 
NULL);
     g_autofree gchar *fifo = g_strdup_printf("%s/%s", tmpdir, TEST_FIFO);
-    g_autoptr(GString) srcargs = g_string_new(socat);
-    g_autoptr(GString) dstargs = g_string_new(socat);
-    g_auto(GStrv) srcargv;
-    g_auto(GStrv) dstargv;
+    g_autofree gchar *srcargs = g_strdup_printf("%s - PIPE:%s,wronly", socat, 
fifo);
+    g_autofree gchar *dstargs = g_strdup_printf("%s PIPE:%s,rdonly -", socat, 
fifo);
+    g_auto(GStrv) srcargv = g_strsplit(srcargs, " ", -1);
+    g_auto(GStrv) dstargv = g_strsplit(dstargs, " ", -1);
     QIOChannel *src, *dst;
     QIOChannelTest *test;
 
-    g_string_append_printf(srcargs, " - PIPE:%s,wronly", fifo);
-    g_string_append_printf(dstargs, " PIPE:%s,rdonly -", fifo);
-
-    srcargv = g_strsplit(srcargs->str, " ", -1);
-    dstargv = g_strsplit(dstargs->str, " ", -1);
-
     src = QIO_CHANNEL(qio_channel_command_new_spawn((const char **) srcargv,
                                                     O_WRONLY,
--8<---------------cut here---------------end--------------->8---




-- 
Alex Bennée