https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115758
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |INVALID
Status|UNCONFIRMED |RESOLVED
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
With -fsanitize=address we get:
=================================================================
==1==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7fe0b0200038
at pc 0x0000004014ca bp 0x7fff659fac90 sp 0x7fff659fac88
READ of size 8 at 0x7fe0b0200038 thread T0
#0 0x4014c9 in n /app/example.c:23
#1 0x4015b7 in main /app/example.c:27
#2 0x7fe0b2029d8f (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f) (BuildId:
490fef8403240c91833978d494d39e537409b92e)
#3 0x7fe0b2029e3f in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x29e3f) (BuildId:
490fef8403240c91833978d494d39e537409b92e)
#4 0x401104 in _start (/app/output.s+0x401104) (BuildId:
f7cb729e32f54ad4816d1652d974eca432f8f942)
Address 0x7fe0b0200038 is located in stack of thread T0 at offset 56 in frame
#0 0x4011d5 in n /app/example.c:13
This frame has 2 object(s):
[32, 88) 'p' (line 16) <== Memory access at offset 56 is inside this
variable
[128, 416) 'r' (line 18)
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 /app/example.c:23 in n
Shadow bytes around the buggy address:
0x7fe0b01ffd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x7fe0b01ffe00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x7fe0b01ffe80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x7fe0b01fff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x7fe0b01fff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x7fe0b0200000: f1 f1 f1 f1 f8 f8 f8[f8]f8 f8 f8 f2 f2 f2 f2 f2
0x7fe0b0200080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x7fe0b0200100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x7fe0b0200180: 00 00 00 00 f3 f3 f3 f3 f3 f3 f3 f3 00 00 00 00
0x7fe0b0200200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x7fe0b0200280: 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
==1==ABORTING
Which is what I expected as p goes out of scope and you access it via **m .
