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math: fix undefined shift in logf

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A signed int shift overflowed when computing a constant mask, use hex
literal instead.  This is unlikely to cause actual issues unless the
code was compiled with ubsan or similar instrumentation specifically
to catch this. The stripped libc.so is unchanged on x86_64.
Reported by q66 on irc.
This commit is contained in:
Szabolcs Nagy 2023-01-20 11:37:39 +01:00 • committed by Rich Felker
parent 7e13e5ae69
commit 35fdfe62a4
1 changed files with 1 additions and 1 deletions
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2
src/math/logf.c
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@ -53,7 +53,7 @@ float logf(float x)
tmp = ix - OFF;
i = (tmp >> (23 - LOGF_TABLE_BITS)) % N;
k = (int32_t)tmp >> 23; /* arithmetic shift */
iz = ix - (tmp & 0x1ff << 23);
iz = ix - (tmp & 0xff800000);
invc = T[i].invc;
logc = T[i].logc;
z = (double_t)asfloat(iz);