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Fix compile errors with gcc 14 #1176

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Fix compile errors with gcc 14 #1176

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@bkuhls bkuhls commented Nov 15, 2025

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hfiguiere
hfiguiere reviewed Nov 15, 2025
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hfiguiere
hfiguiere reviewed Nov 15, 2025
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@bkuhls
ptp2: fix -Wincompatible-pointer-types compiler error in chdk.c
e3b7d7a 
Fixes build error seen with gcc 14.3.0:

ptp2/chdk.c: In function 'yuv_live_to_jpeg':
ptp2/chdk.c:1182:41: error: passing argument 3 of 'jpeg_mem_dest' from incompatible pointer type [-Wincompatible-pointer-types]
 1182 |         jpeg_mem_dest (&cinfo, &outbuf, &outlen);
      |                                         ^~~~~~~
      |                                         |
      |                                         long unsigned int *
In file included from ptp2/chdk.c:32:
/home/autobuild/autobuild/instance-4/output-1/host/mips64el-buildroot-linux-uclibc/sysroot/usr/include/jpeglib.h:979:28: note: expected 'size_t *' {aka 'unsigned int *'} but argument is of type 'long unsigned int *'
  979 | EXTERN(void) jpeg_mem_dest JPP((j_compress_ptr cinfo,
@bkuhls
jl2005c: fix -Wincompatible-pointer-types compiler error in jl2005bcd…
360909c 
…_decompress.c

Seen with gcc 14.3.0:

jl2005c/jl2005bcd_decompress.c: In function 'jl2005bcd_decompress':
jl2005c/jl2005bcd_decompress.c:161:46: error: passing argument 3 of 'jpeg_mem_dest' from incompatible pointer type [-Wincompatible-pointer-types]
  161 |         jpeg_mem_dest (&cinfo, &jpeg_header, &jpeg_header_size);
      |                                              ^~~~~~~~~~~~~~~~~
      |                                              |
      |                                              long unsigned int *
In file included from jl2005c/jpeg_memsrcdest.h:4,
                 from jl2005c/jl2005bcd_decompress.c:39:
/home/autobuild/autobuild/instance-4/output-1/host/mips64el-buildroot-linux-uclibc/sysroot/usr/include/jpeglib.h:979:28: note: expected 'size_t *' {aka 'unsigned int *'} but argument is of type 'long unsigned int *'
  979 | EXTERN(void) jpeg_mem_dest JPP((j_compress_ptr cinfo,
@edgar-bonet
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edgar-bonet commented Nov 16, 2025 •
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The compilation error @bkuhls is referring to happened on the Buildroot auto-builders, while compiling for Linux with uClibc for mips64el:

jl2005c/jl2005bcd_decompress.c:161:46: error: passing argument 3 of 'jpeg_mem_dest' from incompatible pointer type [-Wincompatible-pointer-types]
  161 |         jpeg_mem_dest (&cinfo, &jpeg_header, &jpeg_header_size);
      |                                              ^~~~~~~~~~~~~~~~~
      |                                              |
      |                                              long unsigned int *
In file included from jl2005c/jpeg_memsrcdest.h:4,
                 from jl2005c/jl2005bcd_decompress.c:39:
…/sysroot/usr/include/jpeglib.h:979:28: note: expected 'size_t *' {aka 'unsigned int *'} but argument is of type 'long unsigned int *'
  979 | EXTERN(void) jpeg_mem_dest JPP((j_compress_ptr cinfo,
      |                            ^~~

As shown by this error message, the variable jpeg_header_size is being passed (by address) as the last argument of jpeg_mem_dest(), thus its type should match the type expected by that function, which here is size_t (aka unsigned int).

This pull request presumably fixes the issue on Linux/mips64el. However, it breaks the build with GCC 14 on Linux/x86_64:

jl2005c/jl2005bcd_decompress.c: In function 'jl2005bcd_decompress':
jl2005c/jl2005bcd_decompress.c:161:46: error: passing argument 3 of 'jpeg_mem_dest' from incompatible pointer type [-Wincompatible-pointer-types]
  161 |         jpeg_mem_dest (&cinfo, &jpeg_header, &jpeg_header_size);
      |                                              ^~~~~~~~~~~~~~~~~
      |                                              |
      |                                              uint32_t * {aka unsigned int *}
In file included from jl2005c/jpeg_memsrcdest.h:4,
                 from jl2005c/jl2005bcd_decompress.c:39:
/usr/include/jpeglib.h:979:28: note: expected 'size_t *' {aka 'long unsigned int *'} but argument is of type 'uint32_t *' {aka 'unsigned int *'}

In order to build on every platform, the type of the variable should be exactly what is written in the prototype of jpeg_mem_dest(), and not some platform-dependent synonym. Now, the problem is this type depends on which implementation of jpeg_mem_dest() is being used:

  • libjpeg 9 expects, as seen here, size_t
  • libjpeg 8 and jpeg-turbo expect unsigned long
  • libjpeg <8 does not provide this function. In this case libgphoto2 uses its own implementation, which expects unsigned long.

A general solution would probably require conditional compilation, maybe checking both JPEG_LIB_VERSION and LIBJPEG_TURBO_VERSION.

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@bkuhls @edgar-bonet @hfiguiere