Triggered by scan-13.9 on 9.0. -fsanitize=signed-integer-overflow error for 32-bit long:

generic/tclScan.c:321:15: runtime error: signed integer overflow: -2147483648 - 1 cannot be represented in type 'long int'

Be aware that UBSan says to avoid -lubsan; using gcc or clang as the linker with -fsanitize=undefned should be enough.

Fixed in all three branches. Serendipity that one of the other bugs I was looking at affected 8.6 as well.

Tested with `../configure CFLAGS="-m32 -fsanitize=signed-integer-overflow" LDFLAGS="-lubsan"` (and patched dltest Makefile) but please test and re-open if issue persists.

Thanks for the patch.

(Not saying it's unimportant but my focus is on other areas for the moment)

Fixed the commit message. As for 8.6, 8.7, that would have to wait I'm afraid just as a matter of priority.

Reopening because I would still like for this to be fixed in 8.6 and 8.7.

See attached patch for core-8-6-branch. (For core-8-branch, [3da8d2069c69] can be applied directly along with copying over scan-13.9. But for 8.6, I am not sure anyone would want to bring back compat/strtoull.c, which was removed in 2007.) I agree that storing the result of strtoul() in a signed int caused several issues, including large arguments being erroneously accepted due to truncation from 64-bit to 32-bit, the comment about value/longval being “guaranteed to be > 0” not being true, and the signed integer overflow and the scan-13.9 crash.

To clarify, the overflow is detected by UBSan (UndefinedBehaviorSanitizer) rather than ASan (AddressSanitizer); consider revising the check-in message for [787712b4c733] and [3da8d2069c69].

ASan, like Valgrind, is really only useful with PURIFY defined. I usually configure with both UBSan and ASan enabled, using CFLAGS='-DPURIFY -fsanitize=address -fsanitize=undefined' LDFLAGS='-fsanitize=address' ./configure --enable-symbols … ; I haven’t had to specify -fsanitize=undefined in LDFLAGS so far. I also apply a workaround for [ac874937c5]. I then usually run with ASAN_OPTIONS=allocator_may_return_null=1:detect_leaks=0:malloc_context_size=99.

Fixed in [3da8d2069c]. Verified on Ubuntu 20.

Proposed fix in [bug-ab123cfd3d].

That error sounds like -fsanitize=undefined might need to be added to LDFLAGS.

Fix seems simple but I'd like to reproduce the issue first so I can verify. Could you let me know the configure command for the build? I get a "undefined reference to __ubsan_handle_add_overflow" link error. Sorry, not familiar with address sanitizer.

This issue as well as [d4ede611a7a7] are present on 8.6 and 8.7, as revealed by running the contents of scan-13.9 (scan abc {%2147483648$s}):

tcl86/generic/tclScan.c:318:15: runtime error: signed integer overflow: -2147483648 - 1 cannot be represented in type 'int'
tcl86/generic/tclScan.c:495:14: runtime error: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
tcl86/generic/tclScan.c:684:12: runtime error: signed integer overflow: -2147483648 - 1 cannot be represented in type 'long int'
tcl86/generic/tclScan.c:840:16: runtime error: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
tcl86/generic/tclScan.c:840:7: runtime error: applying non-zero offset 4294967292 to null pointer
AddressSanitizer:DEADLYSIGNAL
=================================================================
==14995==ERROR: AddressSanitizer: SEGV on unknown address 0x3fffffff (pc 0xb638796b bp 0xbf88eed8 sp 0xbf88ecd0 T0)
==14995==The signal is caused by a READ memory access.
    #0 0xb638796b in Tcl_ScanObjCmd tcl86/generic/tclScan.c:840
    #1 0xb5a80a1c in Dispatch tcl86/generic/tclBasic.c:4467
    #2 0xb5a80e22 in TclNRRunCallbacks tcl86/generic/tclBasic.c:4503
    #3 0xb5a7dbc3 in Tcl_EvalObjv tcl86/generic/tclBasic.c:4226
    #4 0xb5a8c904 in TclEvalEx tcl86/generic/tclBasic.c:5372
    #5 0xb6267bdb in Tcl_FSEvalFileEx tcl86/generic/tclIOUtil.c:1824
    #6 0xb62a34b2 in Tcl_MainEx tcl86/generic/tclMain.c:403
    #7 0x509523 in main tcl86/unix/tclAppInit.c:91
    #8 0xb4a25128  (/usr/lib/libc.so.6+0x1f128)
    #9 0xb4a251fc in __libc_start_main (/usr/lib/libc.so.6+0x1f1fc)
    #10 0x5093ea in _start (tcl86/unix/tcltest+0x443ea)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV tcl86/generic/tclScan.c:840 in Tcl_ScanObjCmd
==14995==ABORTING