https://bugs.kde.org/show_bug.cgi?id=420780
Bug ID: 420780
Summary: PPCle erroneous report on strncmp use.
Product: valgrind
Version: 3.15 SVN
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: memcheck
Assignee: jsew...@acm.org
Reporter: ru...@rustcorp.com.au
Target Milestone: ---
SUMMARY
Both valgrind 3.15 and git (60a7ebedc0b53e2cdcea112635a285d8136b68a8) report an
error. This seems similar to https://bugs.kde.org/show_bug.cgi?id=386945
Reduced from a real test cast at
https://github.com/ElementsProject/lightning/issues/3672
/* Compile with -O3 */
#include <string.h>
#include <stdint.h>
int main(int argc, char *argv[])
{
char *s = strdup("02aaa2010000000");
for (size_t i = 0; i < strlen(s); i++) {
if (!strncmp(s + i, " * ", 3))
return 1;
}
return 0;
}
STEPS TO REPRODUCE
1. Enter the above trivial program, and compile with -O3.
2. Run valgrind ./test-valgrind
OBSERVED RESULT
==12951== Memcheck, a memory error detector
==12951== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==12951== Using Valgrind-3.16.0.GIT and LibVEX; rerun with -h for copyright
info
==12951== Command: ./test-valgrind
==12951==
==12951== Invalid read of size 4
==12951== at 0x180774: main (in /home/rusty/test-valgrind)
==12951== Address 0x4b1004d is 13 bytes inside a block of size 16 alloc'd
==12951== at 0x48942AC: malloc (vg_replace_malloc.c:307)
==12951== by 0x499C5E3: strdup (strdup.c:42)
==12951== by 0x18071B: main (in /home/rusty/test-valgrind)
==12951==
==12951==
==12951== HEAP SUMMARY:
==12951== in use at exit: 16 bytes in 1 blocks
==12951== total heap usage: 1 allocs, 0 frees, 16 bytes allocated
==12951==
==12951== LEAK SUMMARY:
==12951== definitely lost: 16 bytes in 1 blocks
==12951== indirectly lost: 0 bytes in 0 blocks
==12951== possibly lost: 0 bytes in 0 blocks
==12951== still reachable: 0 bytes in 0 blocks
==12951== suppressed: 0 bytes in 0 blocks
==12951== Rerun with --leak-check=full to see details of leaked memory
==12951==
==12951== For lists of detected and suppressed errors, rerun with: -s
==12951== ERROR SUMMARY: 2 errors from 1 contexts (suppressed: 0 from 0)
EXPECTED RESULT
No error (except the memleak, sure).
SOFTWARE/OS VERSIONS
Linux falco.openpower.xyz 4.15.0-76-generic #86-Ubuntu SMP Fri Jan 17 17:24:13
UTC 2020 ppc64le ppc64le ppc64le GNU/Linux
libc6 version: 2.27-3ubuntu1
ADDITIONAL INFORMATION
Here's the assembler from gcc -S:
.file "test-valgrind.c"
.abiversion 2
.section ".text"
.globl strncmp
.section .text.startup,"ax",@progbits
.align 2
.p2align 4,,15
.globl main
.type main, @function
main:
.LCF0:
0: addis 2,12,.TOC.-.LCF0@ha
addi 2,2,.TOC.-.LCF0@l
.localentry main,.-main
mflr 0
std 28,-32(1)
std 29,-24(1)
addis 3,2,.LC0@toc@ha
std 30,-16(1)
std 31,-8(1)
addi 3,3,.LC0@toc@l
addis 30,2,.LC1@toc@ha
addi 30,30,.LC1@toc@l
li 28,0
std 0,16(1)
stdu 1,-64(1)
bl strdup
nop
mr 31,3
bl strlen
nop
add 29,31,3
b .L2
.p2align 4,,15
.L17:
bl strncmp
nop
.L4:
cmpwi 7,3,0
addi 31,31,1
beq 7,.L9
.L2:
cmpld 5,31,29
rldicl 9,31,0,52
cmpdi 7,9,4092
li 5,3
mr 4,30
mr 3,31
beq 5,.L16
bge 7,.L17
lwbrx 9,0,31
lwbrx 10,0,30
rldicr 9,9,32,23
rldicr 10,10,32,23
subf. 3,10,9
cmpb 8,9,10
cmpb 7,9,28
orc 8,7,8
cntlzd 8,8
beq 0,.L4
addi 8,8,8
addi 31,31,1
rldcl 3,9,8,56
rldcl 10,10,8,56
subf 3,10,3
cmpwi 7,3,0
bne 7,.L2
.L9:
li 3,1
b .L7
.L16:
li 3,0
.L7:
addi 1,1,64
ld 0,16(1)
ld 28,-32(1)
ld 29,-24(1)
ld 30,-16(1)
ld 31,-8(1)
mtlr 0
blr
.long 0
.byte 0,0,0,1,128,4,0,0
.size main,.-main
.section .rodata.str1.8,"aMS",@progbits,1
.align 3
.LC0:
.string "02aaa2010000000"
.LC1:
.string " * "
.ident "GCC: (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0"
.section .note.GNU-stack,"",@progbits
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