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win32: allow build with USE_ITHREADS=undef but USE_IMP_SYS=define #23178

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Merged
tonycoz merged 5 commits into from
Jul 23, 2025
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win32: allow build with USE_ITHREADS=undef but USE_IMP_SYS=define #23178

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937d799
win32: build without threads but still with implicit sys
tonycoz Apr 3, 2025
8d33f0f
perldelta for Win32 -Dusethreads builds fix
tonycoz Apr 7, 2025
29a96c3
win32_checkTLS: eliminate no longer used variable
tonycoz Apr 7, 2025
8ecfcfb
win32_checkTLS: add a panic message and break into the debugger
tonycoz Apr 8, 2025
3ff321e
win32_checkTLS(): nothing to do without at least multiplicity
tonycoz Apr 9, 2025
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5 changes: 3 additions & 2 deletions pod/perldelta.pod
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Original file line number Diff line number Diff line change
Expand Up @@ -330,9 +330,10 @@ L</Modules and Pragmata> section.

=over 4

=item XXX-some-platform
=item Win32

XXX
Fix builds with C<USE_IMP_SYS> defined but C<USE_ITHREADS> not
defined.

=back

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8 changes: 8 additions & 0 deletions win32/perllib.c
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Expand Up @@ -51,6 +51,7 @@ xs_init(pTHX)
void
win32_checkTLS(PerlInterpreter *host_perl)
{
#ifdef USE_ITHREADS
/* GCurThdId() is lightweight, but b/c of the ctrl-c/signals sometimes firing
in other random WinOS threads, that make the TIDs go out of sync.
This isn't always an error, although high chance of a SEGV in the next
Expand All @@ -67,6 +68,13 @@ win32_checkTLS(PerlInterpreter *host_perl)
}
host_perl->Isys_intern.cur_tid = tid;
}
#else
dTHX;
if (host_perl != my_perl) {
int *nowhere = NULL;
abort();
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@bulk88 bulk88 Apr 8, 2025

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I have zero trust, in ascii token abort() safely stopping all execution of (P5P || CPAN XS author || end user || random 3rd party .dll) controlled (PP || C || C++) code in a Win32 process.

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@bulk88 bulk88 Apr 8, 2025 •
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I have zero trust, in ascii token abort() safely stopping all execution of (P5P || CPAN XS author || end user || random 3rd party .dll) controlled (PP || C || C++) code in a Win32 process.

MS SDL security policy says abort() is forbidden to be used if a perma-assert() decides blackhat machine code is executing inside a Win32 process. Win 8 or Win 10 kernel introduced a user mode __fastfail() x86/x64/ARM CPU opcode to guarantee a Win32 process and its address space 100% stops all execution.

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@bulk88 bulk88 Apr 8, 2025

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Poking around inside machine code of msvcrt.dll shows, libc abort(), can theoretically resume PP code execution through PP's %SIG by executing MS CRT's libc's abort extern C function, plus MS CRT's abort sends out SEH "events" to all active listening registered SEH handlers in the process. 95%-100% of "all active listening registered SEH handlers" are usually exception frames created by C++ lang's try/catch/throw keywords, even WinPerl with P5P default build config out of the box, adds its own SEH event listener callback, with a requested priority of 'Z', so it runs as later as technologically possible, after all C++/C89 try/throw/catch stuff executed, and as the very very last catch frame, before WinOS Kernel draws the WER crash GUI popup box.

Although MS's SEH exception events/dispatch API is language neutral and available in Win32/64 assembly and ISO C89 lang code if someone wants to use the SEH API, 99% of real life catch frames will be random C++ lang code. But the problem is, from my opinion, P5P/me/no developer on earth, knows at "HW fault throw" time, or "SEGV event callback event listener invoke loop time", how many, if any, and where those exception frames came from, or who/what in virtual address space, put their callbacks on the non-public Win Kernel event listener array of things that want to listen to the Win Kernel's SEGV event queue in user mode. So something like MS CRT's "abort()", which uses "warning class (0x4____)" error 0x40000015 STATUS_FATAL_APP_EXIT, something in the SEH stack might have the bright idea to trap/resume, because its 0x4___ "warning class error" which supposedly means "informational" and "normal control flow sometimes"

And abort() isn't using a "0x8___" class error which means (corrupt || unknown || invalid || junk bytes || freed) (object instance || handle || FD || obj ptr)

or the 0xC___ class errors, which are "call 911/112" emergencies, since these are unrecoverable physical hardware errors, SEGVs, SIGILL, SIGBUS, integer div by zero, HW FP math exceptions, or a PCIe device disappeared from the PCIe bus randomly, etc. Nobody, even as a 1st timer coder, would try to trap resume those 0xC___ errors/or the NTSTATUS .h C constants behind those 0xC___ codes at runtime, and anything who knows what the 0xC___ class codes even are, knows what they are doing if they test for them in a SEH catch filter block.

Don't quote me, and I don't feel like googling it, but some, maybe upto half the 0xC___ codes, are documented by MS as non-resumable even if the catch block specifically ask the OS to resume execution with its (end user supplied) CPU register context state snapshot. But remember, nothing will stop a catch block, from synchronously, in normal C89, from executing a Perl_call_sv(); and letting some PP code execute ;-)

whats wrong with writing a Win32 C debugger in Pure Perl and publishing it on CPAN? Nothing, it could be a 100% legit useful CPAN tool lol.

}
#endif
}

EXTERN_C void
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