On 5/3/20 4:32 AM, Philippe Mathieu-Daudé wrote: > When building with Clang 10 on Fedora 32, we get: > > CC audio/mixeng.o > audio/mixeng.c:274:34: error: implicit conversion from 'unsigned int' to > 'float' changes value from 4294967295 to 4294967296 > [-Werror,-Wimplicit-int-float-conversion] > static const float float_scale = UINT_MAX / 2.f; > ^~~~~~~~ ~ > /usr/lib64/clang/10.0.0/include/limits.h:56:37: note: expanded from macro > 'UINT_MAX' > #define UINT_MAX (__INT_MAX__ *2U +1U) > ~~~~~~~~~~~~~~~~~^~~ > > Fix by using a 64-bit float for the conversion, before casting > back to 32-bit float. > > Signed-off-by: Philippe Mathieu-Daudé <f4...@amsat.org> > --- > audio/mixeng.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-)
No, this should be fixed properly. First, the warning is in the !FLOAT_MIXENG branch. IMO that means we should not be using floating point at all, and this should be a simple integral multiply/shift. I had a brief look at this before the 5.0 release. The arithmetic all through audio looks confused to me. There's a combination of shifting and masking (implying a scale by 1<<32), and multiplication and division by UINT32_MAX. I'm reasonably certain that every appearance of UINT32_MAX in this code is an off-by-one bug, or a misuse of the constant. r~
