unused-parameter errors

[christianrauch]

The meson project is built with warnings as errors:

libpisp/meson.build

Lines 7 to 12 in 5042631

	default_options : [
	'werror=true',
	'warning_level=2',
	'cpp_std=c++17',
	'buildtype=release',
	],

Since the code contains unused variables, this causes compilation errors:

FAILED: subprojects/libpisp/src/libpisp.so.1.2.0.p/libpisp_backend_backend_prepare.cpp.o 
ccache c++ [...]
../subprojects/libpisp/src/libpisp/backend/backend_prepare.cpp: In function ‘void {anonymous}::finalise_lsc(pisp_be_lsc_config&, pisp_be_lsc_extra&, uint16_t, uint16_t)’:
../subprojects/libpisp/src/libpisp/backend/backend_prepare.cpp:87:63: error: unused parameter ‘lsc_extra’ [-Werror=unused-parameter]
    87 | void finalise_lsc(pisp_be_lsc_config &lsc, pisp_be_lsc_extra &lsc_extra, uint16_t width, uint16_t height)
      |                                            ~~~~~~~~~~~~~~~~~~~^~~~~~~~~
../subprojects/libpisp/src/libpisp/backend/backend_prepare.cpp: In function ‘void {anonymous}::finalise_cac(pisp_be_cac_config&, pisp_be_cac_extra&, uint16_t, uint16_t)’:
../subprojects/libpisp/src/libpisp/backend/backend_prepare.cpp:101:63: error: unused parameter ‘cac_extra’ [-Werror=unused-parameter]
  101 | void finalise_cac(pisp_be_cac_config &cac, pisp_be_cac_extra &cac_extra, uint16_t width, uint16_t height)
      |                                            ~~~~~~~~~~~~~~~~~~~^~~~~~~~~
cc1plus: all warnings being treated as errors

Shouldn't the CI catch this? How does it come that the CI passes with these defaults?

[naushir]

The lsc_extra does get used, but in an assert in the function. However, my (and the CI) versions of both gcc and clang seems to be fine with that in debug/release build.

What compiler are you using here? If you add [[maybe_unused]] to the parameter, does the warning go away?

[christianrauch]

What compiler are you using here?

This is happening when building a libcamera Debian package for "Ubuntu 24.04" in a chroot with c++ --version -> c++ (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0.

If you add [[maybe_unused]] to the parameter, does the warning go away?

Since this is on CI, I cannot test that easily. But I would assume that maybe_unused fixes that if it is indeed only used in the assert. In any case, it wouldn't hurt to flag possibly unused parameters.

[naushir]

Should be fixed with #43.

[christianrauch]

Should be fixed with #43.

That PR seems to fix the issue I observed. I checked my CI pipeline on libcamera with an updated wrap file that points to your PR branch.

[naushir]

This is now merged.