On 03/29/2012 09:44 AM, Jakub Jelinek wrote:
On Thu, Mar 29, 2012 at 09:05:29AM +0200, Stephan Bergmann wrote:
In LibreOffice's ever-beloved low-level code to synthesize calls to
C++ virtual functions, I'm having the following problem (on Linux
x86_64). The function callVirtualMethod
at<http://cgit.freedesktop.org/libreoffice/core/tree/bridges/source/cpp_uno/gcc3_linux_x86-64/uno2cpp.cxx?id=571876c1234ae55aab0198c7e2caf9049fcd230e#n61>
effectively does the following:
First, call dummy_can_throw_anything that can potentially throw (see
below for why that's there). Second, in an asm block, call some
virtual function (that can potentially throw). Third, call
x86_64::fill_struct that can potentially throw (it doesn't, but
nobody bothered to annotate it as "throw ()").
If the asm isn't in headers, but just in a single short source file
or two, you could try compiling that file with -fnon-call-exceptions.
It is nothing I'd recommend for the whole codebase though.
Turns out I had to move the callVirtualMethod function containing the
asm into a source file of its own, anyway. (Otherwise, even if it no
longer explicitly called functions that can throw, and thus no longer
had corresponding .gcc_except_table entries, exception throwing still
lead to std::terminate. There are other functions in the same source
file callVirtualMethod was originally in that do have .gcc_except_table
entries. Kind of invalidates my previous explanation of why exception
handling bailed out to std::terminate. Looks like I haven't groked it
yet, anyway.)
So an explicit -fnon-call-exceptions on the command line seems to indeed
help. Unfortunately, moving that into a
#pragma GCC optimize ("non-call-exceptions")
at the top of the source file that defines callVirtualMethod (and
nothing more) does *not* work. Is that a bug?
Anyway, would it be worthwhile filing an RFE for an asm annotation
telling the compiler that it contains code that can throw?
Thanks,
Stephan
