https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109470
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
You can use -fsanitize=address to get such bugs diagnosed at runtime:
g++ -fsanitize=address -o /tmp/pr109470{,.C} -g; /tmp/pr109470
=================================================================
==2466554==ERROR: AddressSanitizer: stack-use-after-scope on address
0x7ffe08313d80 at pc 0x000000401304 bp 0x7ffe08313d20 sp 0x7ffe08313d18
READ of size 4 at 0x7ffe08313d80 thread T0
#0 0x401303 in main /tmp/pr109470.C:17
#1 0x7f5b06f7958f in __libc_start_call_main (/lib64/libc.so.6+0x2958f)
#2 0x7f5b06f79648 in __libc_start_main@GLIBC_2.2.5
(/lib64/libc.so.6+0x29648)
#3 0x4010e4 in _start (/tmp/pr109470+0x4010e4)
Address 0x7ffe08313d80 is located in stack of thread T0 at offset 64 in frame
#0 0x4011b5 in main /tmp/pr109470.C:12
This frame has 2 object(s):
[48, 52) 'MAX' (line 14)
[64, 68) '<unknown>' <== Memory access at offset 64 is inside this variable
HINT: this may be a false positive if your program uses some custom stack
unwind mechanism, swapcontext or vfork
(longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-use-after-scope /tmp/pr109470.C:17 in main
Shadow bytes around the buggy address:
0x10004105a760: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10004105a770: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10004105a780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10004105a790: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10004105a7a0: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 f1 f1 04 f2
=>0x10004105a7b0:[f8]f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
0x10004105a7c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10004105a7d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10004105a7e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10004105a7f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10004105a800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
==2466554==ABORTING
C++ has always behaved like this and changing it would significantly penalize
all the code in the wild that uses C++ correctly. There are some exceptions
where the lifetime is extended, but is certainly not one of them.
