From: Gerd Hoffmann <kraxel@redhat.com>
To: qemu-devel@nongnu.org
Cc: "Philippe Mathieu-Daudé" <philmd@redhat.com>,
"Volker Rümelin" <vr_qemu@t-online.de>,
"Markus Armbruster" <armbru@redhat.com>,
"Aleksandar Markovic" <aleksandar.qemu.devel@gmail.com>,
"Gerd Hoffmann" <kraxel@redhat.com>,
"Aleksandar Rikalo" <aleksandar.rikalo@rt-rk.com>,
"Aurelien Jarno" <aurelien@aurel32.net>
Subject: [PULL 4/8] audio/mixeng: fix clang 10+ warning
Date: Tue, 26 May 2020 09:56:35 +0200 [thread overview]
Message-ID: <20200526075639.27949-5-kraxel@redhat.com> (raw)
In-Reply-To: <20200526075639.27949-1-kraxel@redhat.com>
From: Volker Rümelin <vr_qemu@t-online.de>
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>
---
audio/mixeng.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/audio/mixeng.c b/audio/mixeng.c
index 739a500449ce..924dcb858af5 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)
--
2.18.4
next prev parent reply other threads:[~2020-05-26 8:01 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-26 7:56 [PULL 0/8] Audio 20200526 patches Gerd Hoffmann
2020-05-26 7:56 ` [PULL 1/8] es1370: check total frame count against current frame Gerd Hoffmann
2020-05-26 7:56 ` [PULL 2/8] hw/audio/gus: Use AUDIO_HOST_ENDIANNESS definition from 'audio/audio.h' Gerd Hoffmann
2020-05-26 7:56 ` [PULL 3/8] audio/jack: add JACK client audiodev Gerd Hoffmann
2020-05-26 7:56 ` Gerd Hoffmann [this message]
2020-05-26 7:56 ` [PULL 5/8] audio: fix wavcapture segfault Gerd Hoffmann
2020-05-26 7:56 ` [PULL 6/8] audio: Let audio_sample_to_uint64() use const samples argument Gerd Hoffmann
2020-05-26 7:56 ` [PULL 7/8] audio: Let capture_callback handler use const buffer argument Gerd Hoffmann
2020-05-26 7:56 ` [PULL 8/8] hw/mips/mips_fulong2e: Remove unused 'audio/audio.h' include Gerd Hoffmann
2020-05-26 13:05 ` [PULL 0/8] Audio 20200526 patches Peter Maydell
2020-05-27 6:30 ` Markus Armbruster
2020-05-27 9:56 ` Gerd Hoffmann
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