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| author | Volker Rümelin <vr_qemu@t-online.de> | 2020-05-23 22:17:12 +0200 |
|---|---|---|
| committer | Gerd Hoffmann <kraxel@redhat.com> | 2020-05-26 07:46:51 +0200 |
| commit | 9c61fcc89a70256c19047d251aa44f666f06089c (patch) | |
| tree | 58ced41448f18ee53aa763abeb9d18862697806f /audio | |
| parent | 2e44570321056feaa045a51d5e3e8585cea627d0 (diff) | |
| download | qemu-9c61fcc89a70256c19047d251aa44f666f06089c.zip qemu-9c61fcc89a70256c19047d251aa44f666f06089c.tar.gz qemu-9c61fcc89a70256c19047d251aa44f666f06089c.tar.bz2 | |
audio/mixeng: fix clang 10+ warning
The code in CONV_NATURAL_FLOAT() and CLIP_NATURAL_FLOAT()
seems to use the constant 2^31-0.5 to convert float to integer
and back. But the float type lacks the required precision and
the constant used for the conversion is 2^31. This is equiva-
lent to a [-1.f, 1.f] <-> [INT32_MIN, INT32_MAX + 1] mapping.
This patch explicitly writes down the used constant. The
compiler generated code doesn't change.
The constant 2^31 has an exact float representation and the
clang 10 compiler stops complaining about an implicit int to
float conversion with a changed value.
A few notes:
- The conversion of 1.f to INT32_MAX + 1 doesn't overflow. The
type of the destination variable is int64_t.
- At a later stage one of the clip_* functions in
audio/mixeng_template.h limits INT32_MAX + 1 to the integer
range.
- The clip_natural_float_* functions in audio/mixeng.c convert
INT32_MAX and INT32_MAX + 1 to 1.f.
Buglink: https://bugs.launchpad.net/bugs/1878627
Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-id: 20200523201712.23908-1-vr_qemu@t-online.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Diffstat (limited to 'audio')
| -rw-r--r-- | audio/mixeng.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/audio/mixeng.c b/audio/mixeng.c index 739a500..924dcb8 100644 --- a/audio/mixeng.c +++ b/audio/mixeng.c @@ -271,11 +271,12 @@ f_sample *mixeng_clip[2][2][2][3] = { #define CONV_NATURAL_FLOAT(x) (x) #define CLIP_NATURAL_FLOAT(x) (x) #else -static const float float_scale = UINT_MAX / 2.f; +/* macros to map [-1.f, 1.f] <-> [INT32_MIN, INT32_MAX + 1] */ +static const float float_scale = (int64_t)INT32_MAX + 1; #define CONV_NATURAL_FLOAT(x) ((x) * float_scale) #ifdef RECIPROCAL -static const float float_scale_reciprocal = 2.f / UINT_MAX; +static const float float_scale_reciprocal = 1.f / ((int64_t)INT32_MAX + 1); #define CLIP_NATURAL_FLOAT(x) ((x) * float_scale_reciprocal) #else #define CLIP_NATURAL_FLOAT(x) ((x) / float_scale) |