[libcamera-devel] [PATCH v2] qcam: viewfinder_gl: Fix maybe-uninitialized warnings

[Laurent Pinchart]

From: Marco Felsch <m.felsch at pengutronix.de>

Commit 251f0534b74b ("qcam: viewfinder_gl: Take color space into account
for YUV rendering") introduced maybe-uninitialized warnings with gcc 11
and 12 when compiling with -O3. Both compilers warn that

../../src/qcam/viewfinder_gl.cpp: In member function ‘void ViewFinderGL::selectColorSpace(const libcamera::ColorSpace&)’:
../../src/qcam/viewfinder_gl.cpp:392:21: error: ‘offset’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
  391 |         fragmentShaderDefines_.append(QString("#define YUV2RGB_Y_OFFSET %1")
      |                                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  392 |                 .arg(offset, 0, 'f', 1));
      |                 ~~~~^~~~~~~~~~~~~~~~~~~

Additionally, gcc 12 warns that

../../src/qcam/viewfinder_gl.cpp: In member function ‘void ViewFinderGL::selectColorSpace(const libcamera::ColorSpace&)’:
../../src/qcam/viewfinder_gl.cpp:379:36: error: ‘yuv2rgb’ may be used uninitialized [-Werror=maybe-uninitialized]
  379 |                         yuv2rgb[i] *= 255.0 / 219.0;
../../src/qcam/viewfinder_gl.cpp:330:31: note: ‘yuv2rgb’ declared here
  330 |         std::array<double, 9> yuv2rgb;
      |

While this should never happen here, the compiler isn't necessarily
wrong, as C++17 allows initializing a scoped enum from an integer using
direct-list-initialization, even if the integer value doesn't match any
of the enumerators for the scoped enum ([1]). Whether this is valid or
borderline paranoia from gcc may be debatable, but in any case it can't
be classified as blatantly wrong. Fix the warnings by adding default
cases to the switch statements in ViewFinderGL::selectColorSpace().
Which case is selected as the default doesn't matter, as this is not
meant to happen.

[1] https://en.cppreference.com/w/cpp/language/enum#enum_relaxed_init_cpp17

Fixes: 251f0534b74b ("qcam: viewfinder_gl: Take color space into account for YUV rendering")
Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Rewrote commit message, added a default case for the encoding switch.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 src/qcam/viewfinder_gl.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/qcam/viewfinder_gl.cpp b/src/qcam/viewfinder_gl.cpp
index e2aa24703ff0..38ddad58e09e 100644
--- a/src/qcam/viewfinder_gl.cpp
+++ b/src/qcam/viewfinder_gl.cpp
@@ -332,6 +332,7 @@ void ViewFinderGL::selectColorSpace(const libcamera::ColorSpace &colorSpace)
 	/* OpenGL stores arrays in column-major order. */
 	switch (colorSpace.ycbcrEncoding) {
 	case libcamera::ColorSpace::YcbcrEncoding::None:
+	default:
 		yuv2rgb = {
 			1.0000,  0.0000,  0.0000,
 			0.0000,  1.0000,  0.0000,
@@ -368,6 +369,7 @@ void ViewFinderGL::selectColorSpace(const libcamera::ColorSpace &colorSpace)
 
 	switch (colorSpace.range) {
 	case libcamera::ColorSpace::Range::Full:
+	default:
 		offset = 0.0;
 		break;
 

base-commit: 251f0534b74bcb46c777aa0df34b1b4142b664f5
-- 
Regards,

Laurent Pinchart