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exceptions: make the exception handler stack per-thread. 

This prevents the weird failures I saw on macOS in #17856; instead, it
should fail on *all* platforms with

    Unhandled exception ("epan/proto.c:8800: failed assertion "DISSECTOR_ASSERT_NOT_REACHED"", group=1, code=6)

(which it does on macOS 11.6/Xcode 12.5.1 and Windows 10/VS 2019
16.11.8; according to

https://en.wikipedia.org/w/index.php?title=Thread-local_storage&oldid=1064900318#C_and_C++

the major UN*X C compilers support __thread and the major Windows C
compilers support __declspec(thread).).

@jvalverde: on branches that require C11/C++11 support, we could perhaps
just use _Thread_local for C and thread_local for C++.  Note that
<thread.h> is optional in C11, and macOS 11.6/Xcode 12.5.1 does not
appear to include it.)

This does not *fix* the aforementioned issue; to do *that* we need to do
TRY in the register-dissectors thread code.  I'm committing this
separately because it fixes a bug in our exception package that could
cause all sorts of randomness now and in the future - what we're doing
now is Just Wrong.

(Yes, there's code to support per-thread exception handler stacks *on
platforms with pthreads*, but this is simpler *and* also works on
Windows.)
This commit is contained in:
Guy Harris 2022-01-10 13:58:43 -08:00 committed by A Wireshark GitLab Utility
parent b5c51f396a
commit db27fb777a
2 changed files with 18 additions and 1 deletions
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2
epan/except.c
View File

@ -143,7 +143,7 @@ static void (*uh_catcher_ptr)(except_t *) = unhandled_catcher;
* the size_t issue doesn't exists here. Pheew.. */
static void *(*allocator)(size_t) = (void *(*)(size_t)) g_malloc;
static void (*deallocator)(void *) = g_free;
static struct except_stacknode *stack_top;
static WS_THREAD_LOCAL struct except_stacknode *stack_top;
#define get_top() (stack_top)
#define set_top(T) (stack_top = (T))

17
include/ws_attributes.h
View File

@ -75,6 +75,23 @@ extern "C" {
#define WS_RETNONNULL
#endif
/*
* WS_THREAD_LOCAL means "this variable should go in thread-local
* storage.
*
* Based on
*
* https://en.wikipedia.org/w/index.php?title=Thread-local_storage&oldid=1064900318#C_and_C++
*
* the major UN*X C compilers support __thread and the major Windows C
* compilers support __declspec(thread).
*/
#ifdef _WIN32
#define WS_THREAD_LOCAL __declspec(thread)
#else
#define WS_THREAD_LOCAL __thread
#endif
#ifdef __cplusplus
}
#endif /* __cplusplus */