https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122035
--- Comment #12 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Krzysztof Pecka from comment #11)
> Interesting. I honestly forgot about null character.
> Still for me, interesting to see those different behaviors with different
> optimization flags.
Well the behavior is undefined.
Adding `-fsanitize=undefined -fsanitize=address` detects it too:
```
=================================================================
==1==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7a581b800021
at pc 0x7e581e0d0163 bp 0x7ffdd94700c0 sp 0x7ffdd946f890
READ of size 2 at 0x7a581b800021 thread T0
#0 0x7e581e0d0162
(/opt/compiler-explorer/gcc-snapshot/lib64/libasan.so.8+0x88162) (BuildId:
584e3e9072ba505191f9e87a73e5cd97f9c900fd)
#1 0x00000040838c in std::char_traits<char>::length(char const*)
(/app/output.s+0x40838c) (BuildId: b96e3b53f7609bd71442daaaaa201f5f8521b3c9)
#2 0x00000041f7ba in std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> >::find_first_of(char const*,
unsigned long) const (/app/output.s+0x41f7ba) (BuildId:
b96e3b53f7609bd71442daaaaa201f5f8521b3c9)
#3 0x00000040658d in main (/app/output.s+0x40658d) (BuildId:
b96e3b53f7609bd71442daaaaa201f5f8521b3c9)
#4 0x7e581d429d8f (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f) (BuildId:
d5197096f709801829b118af1b7cf6631efa2dcd)
#5 0x7e581d429e3f in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x29e3f) (BuildId:
d5197096f709801829b118af1b7cf6631efa2dcd)
#6 0x000000405744 in _start (/app/output.s+0x405744) (BuildId:
b96e3b53f7609bd71442daaaaa201f5f8521b3c9)
Address 0x7a581b800021 is located in stack of thread T0 at offset 33 in frame
#0 0x000000406373 in main (/app/output.s+0x406373) (BuildId:
b96e3b53f7609bd71442daaaaa201f5f8521b3c9)
This frame has 13 object(s):
[32, 33) 'semicolonChar' (line 42) <== Memory access at offset 33 overflows
this variable
[48, 56) '<unknown>'
[80, 88) '<unknown>'
[112, 120) '__for_begin' (line 77)
[144, 152) '__for_end' (line 77)
[176, 208) 'line' (line 41)
[240, 272) 'stationName' (line 45)
[304, 336) 'strTemp' (line 46)
[368, 400) '<unknown>'
[432, 464) '<unknown>'
[496, 552) 'stations' (line 38)
[592, 656) '<unknown>'
[688, 1080) 'inputFile' (line 39)
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-buffer-overflow (/app/output.s+0x40838c)
(BuildId: b96e3b53f7609bd71442daaaaa201f5f8521b3c9) in
std::char_traits<char>::length(char const*)
Shadow bytes around the buggy address:
0x7a581b7ffd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x7a581b7ffe00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x7a581b7ffe80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x7a581b7fff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x7a581b7fff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x7a581b800000: f1 f1 f1 f1[01]f2 00 f2 f2 f2 00 f2 f2 f2 00 f2
0x7a581b800080: f2 f2 00 f2 f2 f2 00 00 00 00 f2 f2 f2 f2 00 00
0x7a581b800100: 00 00 f2 f2 f2 f2 00 00 00 00 f2 f2 f2 f2 00 00
0x7a581b800180: 00 00 f2 f2 f2 f2 00 00 00 00 f2 f2 f2 f2 00 00
0x7a581b800200: 00 00 00 00 00 f2 f2 f2 f2 f2 00 00 00 00 00 00
0x7a581b800280: 00 00 f2 f2 f2 f2 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
```
