Re: [FFmpeg-devel] [PATCH v19 1/5] libavutil: Add wchartoutf8(), wchartoansi(), utf8toansi(), getenv_utf8() and freeenv_utf8()

["Martin Storsjö" <martin@martin.st>]

On Sun, 19 Jun 2022, Nil Admirari wrote:

> wchartoutf8() converts strings returned by WinAPI into UTF-8,
> which is FFmpeg's preffered encoding.
>
> Some external dependencies, such as AviSynth, are still
> not Unicode-enabled. utf8toansi() converts UTF-8 strings
> into ANSI in two steps: UTF-8 -> wchar_t -> ANSI.
> wchartoansi() is responsible for the second step of the conversion.
> Conversion in just one step is not supported by WinAPI.
>
> Since these character converting functions allocate the buffer
> of necessary size, they also facilitate the removal of MAX_PATH limit
> in places where fixed-size ANSI/WCHAR strings were used
> as filename buffers.
>
> getenv_utf8() wraps _wgetenv() converting its input from
> and its output to UTF-8. Compared to plain getenv(),
> getenv_utf8() requires a cleanup.
>
> Because of that, in places that only test the existence of
> an environment variable or compare its value with a string
> consisting entirely of ASCII characters, the use of plain getenv()
> is still preferred. (libavutil/log.c check_color_terminal()
> is an example of such a place.)
>
> Plain getenv() is also preffered in UNIX-only code,
> such as bktr.c, fbdev_common.c, oss.c in libavdevice
> or af_ladspa.c in libavfilter.
> ---
> configure                  |  1 +
> libavutil/getenv_utf8.h    | 83 ++++++++++++++++++++++++++++++++++++++
> libavutil/wchar_filename.h | 53 ++++++++++++++++++++++++
> 3 files changed, 137 insertions(+)
> create mode 100644 libavutil/getenv_utf8.h

Looks good overall, thanks! The freeenv_utf8 function needed a couple 
minor fixes though, to fix these warnings/errors:

src/libavutil/getenv_utf8.h: In function ‘freeenv_utf8’:
src/libavutil/getenv_utf8.h:59:13: warning: passing argument 1 of 
‘av_free’ discards ‘const’ qualifier from pointer target type 
[-Wdiscarded-qualifiers]
    59 |     av_free(var);


In file included from src/libavformat/http.c:32:
src/libavutil/getenv_utf8.h: In function ‘freeenv_utf8’:
src/libavutil/getenv_utf8.h:69:33: error: parameter name omitted
    69 | static inline void freeenv_utf8(char *)

Fixed locally with these changes:

@@ -54,7 +54,7 @@ static inline char *getenv_utf8(const char *varname)
      // non UTF-8 strings must not be returned.
  }

-static inline void freeenv_utf8(const char *var)
+static inline void freeenv_utf8(char *var)
  {
      av_free(var);
  }
@@ -66,7 +66,7 @@ static inline char *getenv_utf8(const char *varname)
      return getenv(varname);
  }

-static inline void freeenv_utf8(const char *)
+static inline void freeenv_utf8(char *var)
  {
  }

(No need to resend for these changes IMO.)

If there's no further comments, I'd push this set tomorrow, with these 
changes amended.

// Martin
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