[Qemu-devel] [PATCH v2] qemu-config: Accept empty option values

[Qemu-devel] [PATCH v2] qemu-config: Accept empty option values

[Eduardo Habkost]

Currently it is impossible to set an option in a config file to an empty
string, because the parser matches only lines containing non-empty
strings between double-quotes.

As sscanf() "[" conversion specifier only matches non-empty strings, add
a special case for empty strings.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
Changes v1 -> v2:
* Move value[0]='\0' assignment outside if condition. Nobody seemed
  to like the comma operator usage in v1 (including myself), and then I
  noticed that it was also making checkpatch.pl sad.
---
 util/qemu-config.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/util/qemu-config.c b/util/qemu-config.c
index 2d32ce7..a393a3d 100644
--- a/util/qemu-config.c
+++ b/util/qemu-config.c
@@ -413,7 +413,9 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname)
             opts = qemu_opts_create(list, NULL, 0, &error_abort);
             continue;
         }
-        if (sscanf(line, " %63s = \"%1023[^\"]\"", arg, value) == 2) {
+        value[0] = '\0';
+        if (sscanf(line, " %63s = \"%1023[^\"]\"", arg, value) == 2 ||
+            sscanf(line, " %63s = \"\"", arg) == 1) {
             /* arg = value */
             if (opts == NULL) {
                 error_report("no group defined");
-- 
2.1.0

Re: [Qemu-devel] [PATCH v2] qemu-config: Accept empty option values

[Eric Blake]

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On 04/15/2015 05:59 AM, Eduardo Habkost wrote:
> Currently it is impossible to set an option in a config file to an empty
> string, because the parser matches only lines containing non-empty
> strings between double-quotes.
> 
> As sscanf() "[" conversion specifier only matches non-empty strings, add
> a special case for empty strings.
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> Changes v1 -> v2:
> * Move value[0]='\0' assignment outside if condition. Nobody seemed
>   to like the comma operator usage in v1 (including myself), and then I
>   noticed that it was also making checkpatch.pl sad.
> ---
>  util/qemu-config.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

> 
> diff --git a/util/qemu-config.c b/util/qemu-config.c
> index 2d32ce7..a393a3d 100644
> --- a/util/qemu-config.c
> +++ b/util/qemu-config.c
> @@ -413,7 +413,9 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname)
>              opts = qemu_opts_create(list, NULL, 0, &error_abort);
>              continue;
>          }
> -        if (sscanf(line, " %63s = \"%1023[^\"]\"", arg, value) == 2) {
> +        value[0] = '\0';
> +        if (sscanf(line, " %63s = \"%1023[^\"]\"", arg, value) == 2 ||
> +            sscanf(line, " %63s = \"\"", arg) == 1) {
>              /* arg = value */
>              if (opts == NULL) {
>                  error_report("no group defined");
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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