[FFmpeg-devel] fftools/ffmpeg_opt: Fix mixed declarations and code

Submitted by Andreas Rheinhardt on Nov. 6, 2019, 12:18 p.m.

Details

Message ID 20191106121816.23802-1-andreas.rheinhardt@gmail.com
State New
Headers show

Commit Message

Andreas Rheinhardt Nov. 6, 2019, 12:18 p.m.
Introduced in ed3c317d.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
---
 fftools/ffmpeg_opt.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

Michael Niedermayer Nov. 6, 2019, 7:04 p.m.
On Wed, Nov 06, 2019 at 01:18:16PM +0100, Andreas Rheinhardt wrote:
> Introduced in ed3c317d.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
> ---
>  fftools/ffmpeg_opt.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

will apply

thx

[...]
Carl Eugen Hoyos Nov. 6, 2019, 7:08 p.m.
Am Mi., 6. Nov. 2019 um 13:18 Uhr schrieb Andreas Rheinhardt
<andreas.rheinhardt@gmail.com>:
>
> Introduced in ed3c317d.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
> ---
>  fftools/ffmpeg_opt.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
> index af9a9a6acb..f4ccf3f65e 100644
> --- a/fftools/ffmpeg_opt.c
> +++ b/fftools/ffmpeg_opt.c
> @@ -3008,9 +3008,10 @@ static int opt_old2new(void *optctx, const char *opt, const char *arg)
>  {
>      OptionsContext *o = optctx;
>      char *s = av_asprintf("%s:%c", opt + 1, *opt);
> +    int ret;

Shouldn't the new declarations be above the call to av_asprintf()?

Carl Eugen
Michael Niedermayer Nov. 6, 2019, 7:23 p.m.
On Wed, Nov 06, 2019 at 08:08:27PM +0100, Carl Eugen Hoyos wrote:
> Am Mi., 6. Nov. 2019 um 13:18 Uhr schrieb Andreas Rheinhardt
> <andreas.rheinhardt@gmail.com>:
> >
> > Introduced in ed3c317d.
> >
> > Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
> > ---
> >  fftools/ffmpeg_opt.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
> > index af9a9a6acb..f4ccf3f65e 100644
> > --- a/fftools/ffmpeg_opt.c
> > +++ b/fftools/ffmpeg_opt.c
> > @@ -3008,9 +3008,10 @@ static int opt_old2new(void *optctx, const char *opt, const char *arg)
> >  {
> >      OptionsContext *o = optctx;
> >      char *s = av_asprintf("%s:%c", opt + 1, *opt);
> > +    int ret;
> 
> Shouldn't the new declarations be above the call to av_asprintf()?

will apply with that change

thx

[...]
Andreas Rheinhardt Nov. 8, 2019, 1:31 p.m.
Carl Eugen Hoyos:
> Am Mi., 6. Nov. 2019 um 13:18 Uhr schrieb Andreas Rheinhardt
> <andreas.rheinhardt@gmail.com>:
>>
>> Introduced in ed3c317d.
>>
>> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
>> ---
>>  fftools/ffmpeg_opt.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
>> index af9a9a6acb..f4ccf3f65e 100644
>> --- a/fftools/ffmpeg_opt.c
>> +++ b/fftools/ffmpeg_opt.c
>> @@ -3008,9 +3008,10 @@ static int opt_old2new(void *optctx, const char *opt, const char *arg)
>>  {
>>      OptionsContext *o = optctx;
>>      char *s = av_asprintf("%s:%c", opt + 1, *opt);
>> +    int ret;
> 
> Shouldn't the new declarations be above the call to av_asprintf()?
> 
> Carl Eugen

It is completely legal to perform an initialization via function call
in the middle of the declarations. I just reread the (relevant part
of) the standard and here comes the relevant language-lawyer-stuff.

The source of the ban on "mixed declarations and code" in C90 is the
syntax of compound statements (square brackets are used to denote
optional parts):

compound-statement:
    {  [declaration_list] [statement-list]  }

declaration-list
    declaration
    declaration-list declaration

statement-list
    statement
    statement-list statement

And the important parts of declaration are

    declarator = initializer

and

initializer
    assignment-expression
...

The syntax of assignment-expression is this:

assignment-expression:
    conditional-expression
    unary-expression assignment-operator assignment-expression

Now the assignment-expression isn't what one might think: the "="
immediately following the declarator is already used and is therefore
not part of it, so that the first form of assignment-expression is used.
Now comes a series of types of expression that have two forms: One
that one would expect from common usage and a passthrough form. E.g.
here is the syntax for conditional-expression:

conditional-expression:
    logical-OR-expression
    logical-OR-expression ? expression : conditional-expression

Of course the first form is used here. Via passthrough every
logical-OR-expression is a logical-AND-expression is an
inclusive-OR-expression is an exclusive-OR-expression is an
AND-expression is an equality-expression is a relational-expression is
a shift-expression is an additive-expression is a
multiplicative-expression is a cast-expression is a unary-expression
is a postfix-expression. And postfix-expressions have a function-call
form.

- Andreas

Patch hide | download patch | download mbox

diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
index af9a9a6acb..f4ccf3f65e 100644
--- a/fftools/ffmpeg_opt.c
+++ b/fftools/ffmpeg_opt.c
@@ -3008,9 +3008,10 @@  static int opt_old2new(void *optctx, const char *opt, const char *arg)
 {
     OptionsContext *o = optctx;
     char *s = av_asprintf("%s:%c", opt + 1, *opt);
+    int ret;
     if (!s)
         return AVERROR(ENOMEM);
-    int ret = parse_option(o, s, arg, options);
+    ret = parse_option(o, s, arg, options);
     av_free(s);
     return ret;
 }
@@ -3088,9 +3089,10 @@  static int opt_timecode(void *optctx, const char *opt, const char *arg)
 {
     OptionsContext *o = optctx;
     char *tcr = av_asprintf("timecode=%s", arg);
+    int ret;
     if (!tcr)
         return AVERROR(ENOMEM);
-    int ret = parse_option(o, "metadata:g", tcr, options);
+    ret = parse_option(o, "metadata:g", tcr, options);
     if (ret >= 0)
         ret = av_dict_set(&o->g->codec_opts, "gop_timecode", arg, 0);
     av_free(tcr);