- We do some nasty things w.r.t. installing or overriding signal handlers in
order to improve our crash recovery support or interaction with crash
reporting software, and those things are not necessarily appropriate when
LLVM is being linked into a client application that has its own ideas about
how to do things. This gives those clients a way to disable that handling at
build time.
- Currently, the code this guards is all Apple specific, but other platforms
might have the same concerns so I went for a more generic configure
name. Someone who is more familiar with library embedding on Windows can
handle choosing which of the Windows/Signals.inc behaviors might make sense
to go under this flag.
- This also fixes the proper autoconf'ing of ENABLE_BACKTRACES. The code
expects it to be undefined when disabled, but the autoconf check was just
defining it to 0.
llvm-svn: 189694
The llvm::sys::AddSignalHandler function (as well as related routines) in
lib/Support/Unix/Signals.inc currently registers a signal handler routine
via "sigaction". When this handler is called due to a SIGSEGV, SIGILL or
similar signal, it will show a stack backtrace, deactivate the handler,
and then simply return to the operating system. The intent is that the
OS will now retry execution at the same location as before, which ought
to again trigger the same error condition and cause the same signal to be
delivered again. Since the hander is now deactivated, the OS will take
its default action (usually, terminate the program and possibly create
a core dump).
However, this method doesn't work reliably on System Z: With certain
signals (namely SIGILL, SIGFPE, and SIGTRAP), the program counter stored
by the kernel on the signal stack frame (which is the location where
execution will resume) is not the instruction that triggered the fault,
but then instruction *after it*. When the LLVM signal handler simply
returns to the kernel, execution will then resume at *that* address,
which will not trigger the problem again, but simply go on and execute
potentially unrelated code leading to random errors afterwards.
To fix this, the patch simply goes and re-raises the signal in question
directly from the handler instead of returning from it. This is done
only on System Z and only for those signals that have this particular
problem.
llvm-svn: 181010
Remove the use of the 't' length modifier to avoid a gcc warning. Based
on usage, 32 bits of precision is good enough for printing a stack
offset for a stack trace.
't' length modifier isn't in C++03 but it *is* in C++11. Added a FIXME
to reintroduce once LLVM makes the switch to C++11.
Reviewer: gribozavr
llvm-svn: 173711
Sooooo many of these had incorrect or strange main module includes.
I have manually inspected all of these, and fixed the main module
include to be the nearest plausible thing I could find. If you own or
care about any of these source files, I encourage you to take some time
and check that these edits were sensible. I can't have broken anything
(I strictly added headers, and reordered them, never removed), but they
may not be the headers you'd really like to identify as containing the
API being implemented.
Many forward declarations and missing includes were added to a header
files to allow them to parse cleanly when included first. The main
module rule does in fact have its merits. =]
llvm-svn: 169131
whether or not we want to print out backtrace information. Useful
for libraries that don't need backtrace information on a crash.
rdar://11844710
llvm-svn: 164426
This is likely only the tip of the ice berg, but this particular bug
caused any double-free on a glibc system to turn into a deadlock! It is
not generally safe to either allocate or release heap memory from within
the signal handler. The 'pop_back()' in RemoveFilesToRemove was deleting
memory and causing the deadlock. What's worse, eraseFromDisk in PathV1
has lots of allocation and deallocation paths. We even passed 'true' in
a place that would have caused the *signal handler* to try to run the
'system' system call and shell out to 'rm -rf'. That was never going to
work...
This patch switches the file removal to use a vector of strings so that
the exact text needed for the 'unlink' system call can be stored there.
It switches the loop to be a boring indexed loop, and directly calls
unlink without looking at the error. It also works quite hard to ensure
that calling 'c_str()' is safe, by ensuring that the non-signal-handling
code path that manipulates the vector always leaves it in a state where
every element has already had 'c_str()' called at least once.
I dunno exactly how overkill this is, but it fixes the
deadlock-on-double free issue, and seems likely to prevent any other
issues from sneaking up.
Sorry for not having a test case, but I *really* don't know how to test
signal handling code easily....
llvm-svn: 158580
