https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98692
--- Comment #13 from Mark Wielaard <mark at gcc dot gnu.org> ---
I could replicate this with gcc 9.1.1 with the following source:
#define variables (const char* []){ "PK", "KEK", "db"}
int ret, len;
void isVariable(char *var)
{
for (int v = 0; v < 2; v++)
if (__builtin_strncmp(var,variables[v], 2) == 0)
ret = 0;
}
int main(int argc, char* argv[])
{
// __builtin_printf ("argv[0]=%s\n", argv[0]);
isVariable(argv[0]);
len = __builtin_strlen (argv[0]);
return 0;
}
compiled with gcc -g -Os and valgrind from git trunk with --vgdb=full
--track-origins=yes:
==25741== Command: ./a.out
==25741==
==25741== Use of uninitialised value of size 8
==25741== at 0x10000504: main (pr9862.C:16)
==25741== Uninitialised value was created by a stack allocation
==25741== at 0x100006C4: isVariable(char*) (pr9862.C:6)
==25741==
Disassambly of main and isVariable
Dump of assembler code for function main(int, char**):
0x00000000100004e0 <+0>: lis r2,4098
0x00000000100004e4 <+4>: addi r2,r2,32512
0x00000000100004e8 <+8>: mflr r0
0x00000000100004ec <+12>: std r31,-8(r1)
0x00000000100004f0 <+16>: ld r3,0(r4)
0x00000000100004f4 <+20>: mr r31,r4
0x00000000100004f8 <+24>: std r0,16(r1)
0x00000000100004fc <+28>: stdu r1,-48(r1)
0x0000000010000500 <+32>: bl 0x100006b4 <isVariable(char*)+8>
0x0000000010000504 <+36>: ld r3,0(r31)
0x0000000010000508 <+40>: bl 0x100004a0
<00000023.plt_call.strlen@@GLIBC_2.17>
0x000000001000050c <+44>: ld r2,24(r1)
0x0000000010000510 <+48>: nop
0x0000000010000514 <+52>: addi r1,r1,48
0x0000000010000518 <+56>: stw r3,-32452(r2)
0x000000001000051c <+60>: li r3,0
0x0000000010000520 <+64>: b 0x1000086c <_restgpr0_31>
0x0000000010000524 <+68>: .long 0x0
0x0000000010000528 <+72>: .long 0x1000900
0x000000001000052c <+76>: .long 0x180
End of assembler dump.
Dump of assembler code for function isVariable(char*):
0x00000000100006ac <+0>: lis r2,4098
0x00000000100006b0 <+4>: addi r2,r2,32512
0x00000000100006b4 <+8>: mflr r0
0x00000000100006b8 <+12>: addis r9,r2,-2
0x00000000100006bc <+16>: addi r9,r9,-30152
0x00000000100006c0 <+20>: bl 0x10000820 <_savegpr0_25>
0x00000000100006c4 <+24>: stdu r1,-128(r1)
0x00000000100006c8 <+28>: ld r29,0(r9)
0x00000000100006cc <+32>: ld r28,8(r9)
0x00000000100006d0 <+36>: nop
0x00000000100006d4 <+40>: mr r30,r3
0x00000000100006d8 <+44>: ld r27,16(r9)
0x00000000100006dc <+48>: li r31,0
0x00000000100006e0 <+52>: addi r25,r2,-32456
0x00000000100006e4 <+56>: addi r26,r1,32
0x00000000100006e8 <+60>: std r29,32(r1)
0x00000000100006ec <+64>: std r28,40(r1)
0x00000000100006f0 <+68>: rldicr r9,r31,3,60
0x00000000100006f4 <+72>: li r5,2
0x00000000100006f8 <+76>: std r27,48(r1)
0x00000000100006fc <+80>: mr r3,r30
0x0000000010000700 <+84>: ldx r4,r26,r9
0x0000000010000704 <+88>: bl 0x100004c0
<00000023.plt_call.strncmp@@GLIBC_2.17>
0x0000000010000708 <+92>: ld r2,24(r1)
0x000000001000070c <+96>: mr. r9,r3
0x0000000010000710 <+100>: bne 0x10000718 <isVariable(char*)+108>
0x0000000010000714 <+104>: stw r9,0(r25)
0x0000000010000718 <+108>: cmpldi r31,1
0x000000001000071c <+112>: bne 0x10000728 <isVariable(char*)+124>
0x0000000010000720 <+116>: addi r1,r1,128
0x0000000010000724 <+120>: b 0x10000844 <_restgpr0_25>
0x0000000010000728 <+124>: li r31,1
0x000000001000072c <+128>: b 0x100006e8 <isVariable(char*)+60>
0x0000000010000730 <+132>: .long 0x0
0x0000000010000734 <+136>: .long 0x1000900
0x0000000010000738 <+140>: .long 0x780
End of assembler dump.
