[Bug c++/98419] wrong code when destructor of local variable modifies returned object
marxin at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Tue Dec 22 12:36:16 GMT 2020
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98419
Martin Liška <marxin at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |marxin at gcc dot gnu.org
--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
It seems you invoke a use-after-scope:
g++ pr98419.C -fsanitize=address,undefined && ./a.out
=================================================================
==31013==ERROR: AddressSanitizer: stack-use-after-scope on address
0x7fffffffdf30 at pc 0x000000401532 bp 0x7fffffffdec0 sp 0x7fffffffdeb8
WRITE of size 4 at 0x7fffffffdf30 thread T0
#0 0x401531 in B::~B() (/home/marxin/Programming/testcases/a.out+0x401531)
#1 0x401293 in foo() (/home/marxin/Programming/testcases/a.out+0x401293)
#2 0x4012fb in main (/home/marxin/Programming/testcases/a.out+0x4012fb)
#3 0x7ffff676e151 in __libc_start_main (/lib64/libc.so.6+0x28151)
#4 0x4010fd in _start (/home/marxin/Programming/testcases/a.out+0x4010fd)
Address 0x7fffffffdf30 is located in stack of thread T0 at offset 48 in frame
#0 0x4011b5 in foo() (/home/marxin/Programming/testcases/a.out+0x4011b5)
This frame has 2 object(s):
[48, 52) '<unknown>' <== Memory access at offset 48 is inside this variable
[64, 72) 'b' (line 17)
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
(/home/marxin/Programming/testcases/a.out+0x401531) in B::~B()
Shadow bytes around the buggy address:
0x10007fff7b90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10007fff7ba0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10007fff7bb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10007fff7bc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10007fff7bd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x10007fff7be0: f1 f1 f1 f1 f1 f1[f8]f2 00 f3 f3 f3 00 00 00 00
0x10007fff7bf0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10007fff7c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10007fff7c10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10007fff7c20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10007fff7c30: 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
Shadow gap: cc
==31013==ABORTING
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