[FFmpeg-devel] [PATCH 1/5] Change eval internal functions, ff_parse_expr() and ff_parse_and_eval_expr() interface.

[Michael Niedermayer]

On Mon, Apr 12, 2010 at 11:37:01PM +0200, Stefano Sabatini wrote:
> Make them print error messages on the log using a log_ctx rather than
> set a constant error string in the Parser.
> 
> Simplify the interface, and allow the error message to be more
> expressive, as it is not anymore a generic const char * string.
> ---
>  libavcodec/eval.c        |   18 +++++++++---------
>  libavcodec/eval.h        |    8 ++++----
>  libavcodec/opt.c         |    6 ++----
>  libavcodec/ratecontrol.c |    5 ++---
>  4 files changed, 17 insertions(+), 20 deletions(-)
> 
> diff --git a/libavcodec/eval.c b/libavcodec/eval.c
> index 0b2aed9..0149a55 100644
> --- a/libavcodec/eval.c
> +++ b/libavcodec/eval.c
> @@ -39,7 +39,7 @@ typedef struct Parser{
>      double (* const *func2)(void *, double a, double b); // NULL terminated
>      const char * const *func2_name;          // NULL terminated
>      void *opaque;
> -    const char **error;
> +    void *log_ctx;
>  #define VARS 10
>      double var[VARS];
>  } Parser;
> @@ -201,7 +201,7 @@ static AVExpr * parse_primary(Parser *p) {
>  
>      p->s= strchr(p->s, '(');
>      if(p->s==NULL){
> -        *p->error = "undefined constant or missing (";
> +        av_log(p->log_ctx, AV_LOG_ERROR, "undefined constant or missing (\n");

this patch (not this change specifically) causes problems
one no longer can evaluate an expression without spamming the user
thats all fine if what is evaluated is a user supplied string, for other
cases though it is not appropriate.
If av_log() is used then we need a way to put a limit on the error level
an error for evaluation may or may not be an error for the calling code.
maybe we can just add an 8 entry array to AVClass and use that to
remap the error levels. With that eval would in this case need to
be run on a custom object with an AVClass that silences it.
Thats a quite generic solution (that likely will come in handy
for other code outside evel) but maybe its not the simplest solution

the next obvious alternative is to leave the returning of error messages
as it is.



[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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