From 15acdb8e79fbd8e0456ffe913c207deb39443a88 Mon Sep 17 00:00:00 2001
From: Petter Reinholdtsen <pere@debian.org>
Date: Sun, 9 Mar 2025 14:16:12 +0100
Subject: [PATCH] Avoided undefined bit shifting of signed value.
Use multiplication instead, allowing the compiler to optimize to
bitshifts if it believe it to be safe.
Fixes a few issues discovered by --enable-gcc-sanitize-address in !31.
---
lib/mathops.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/lib/mathops.c b/lib/mathops.c
index 23c8f6e1..aadaa22a 100644
--- a/lib/mathops.c
+++ b/lib/mathops.c
@@ -160,7 +160,7 @@ ogg_int64_t oc_bexp64(ogg_int64_t _z){
/*z is the fractional part of the log in Q62 format.
We need 1 bit of headroom since the magnitude can get larger than 1
during the iteration, and a sign bit.*/
- z<<=5;
+ z*=32;
/*w is the exponential in Q61 format (since it also needs headroom and can
get as large as 2.0); we could get another bit if we dropped the sign,
but we'll recover that bit later anyway.
@@ -175,7 +175,7 @@ ogg_int64_t oc_bexp64(ogg_int64_t _z){
z-=OC_ATANH_LOG2[i]+mask^mask;
/*Repeat iteration 4.*/
if(i>=3)break;
- z<<=1;
+ z*=2;
}
for(;;i++){
mask=-(z<0);
@@ -183,12 +183,12 @@ ogg_int64_t oc_bexp64(ogg_int64_t _z){
z-=OC_ATANH_LOG2[i]+mask^mask;
/*Repeat iteration 13.*/
if(i>=12)break;
- z<<=1;
+ z*=2;
}
for(;i<32;i++){
mask=-(z<0);
w+=(w>>i+1)+mask^mask;
- z=z-(OC_ATANH_LOG2[i]+mask^mask)<<1;
+ z=(z-(OC_ATANH_LOG2[i]+mask^mask))*2;
}
wlo=0;
/*Skip the remaining iterations unless we really require that much
@@ -207,12 +207,12 @@ ogg_int64_t oc_bexp64(ogg_int64_t _z){
z-=OC_ATANH_LOG2[31]+mask^mask;
/*Repeat iteration 40.*/
if(i>=39)break;
- z<<=1;
+ z*=2;
}
for(;i<61;i++){
mask=-(z<0);
wlo+=(w>>i)+mask^mask;
- z=z-(OC_ATANH_LOG2[31]+mask^mask)<<1;
+ z=(z-(OC_ATANH_LOG2[31]+mask^mask))*2;
}
}
w=(w<<1)+wlo;
--
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