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Re: [PATCH] libstdc++: Fix exceptions being generated when compiling with -fno-exceptions
- From: Jonathan Wakely <jwakely at redhat dot com>
- To: Federico Lenarduzzi <federico dot lenarduzzi at tallertechnologies dot com>
- Cc: libstdc++ at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
- Date: Mon, 27 Apr 2015 22:06:28 +0100
- Subject: Re: [PATCH] libstdc++: Fix exceptions being generated when compiling with -fno-exceptions
- Authentication-results: sourceware.org; auth=none
- References: <1429024679-17856-1-git-send-email-federico dot lenarduzzi at tallertechnologies dot com>
On 14/04/15 12:17 -0300, Federico Lenarduzzi wrote:
When the libstdc++ is compiled, the compiler sets the std::terminate_handler function with __verbose_terminate_handler() or std::abort() depending on _GLIBCXX_HOSTED && _GLIBCXX_VERBOSE being true or false.
However, even if we compile with -fno-exceptions, the compiler will use __verbose_terminate_handler(), which uses exceptions. Therefore, the library is not fully exception-free.
This patch adds a check for __EXCEPTIONS to the #if _GLIBCXX_HOSTED && _GLIBCXX_VERBOSE condition. If __EXCEPTIONS is defined, the compiler will use __verbose_terminate_handler() as a termination function; otherwise it'll use std::abort() which doesn't have exceptions. It also makes std::uncaught_exception() throw() return false if __EXCEPTIONS is not defined.
I've committed this slightly revised version using __cpp_exceptions
instead, and changing the new std::uncaught_exceptions() function too.
Tested x86_64-linux and powerpc64le-linux, and also built with
--enable-libstdcxx-flags=-fno-exceptions on x86_64-linux.
commit 80bc538bd64c7f6b9a21ec5d1a3bc5b08bc8770b
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Mon Apr 27 14:04:50 2015 +0100
2015-04-27 Federico Lenarduzzi <federico.lenarduzzi@tallertechnologies.com>
Jonathan Wakely <jwakely@redhat.com>
* libsupc++/eh_catch.cc (uncaught_exception, uncaught_exceptions):
Return false or zero if the library is built without exceptions.
* libsupc++/eh_term_handler.cc: Disable verbose terminate handler if
the library is built without exceptions.
diff --git a/libstdc++-v3/libsupc++/eh_catch.cc b/libstdc++-v3/libsupc++/eh_catch.cc
index 723ae56..44fde79 100644
--- a/libstdc++-v3/libsupc++/eh_catch.cc
+++ b/libstdc++-v3/libsupc++/eh_catch.cc
@@ -136,13 +136,21 @@ __cxxabiv1::__cxa_end_catch ()
bool
std::uncaught_exception() throw()
{
+#if __cpp_exceptions
__cxa_eh_globals *globals = __cxa_get_globals ();
return globals->uncaughtExceptions != 0;
+#else
+ return false;
+#endif
}
int
std::uncaught_exceptions() throw()
{
+#if __cpp_exceptions
__cxa_eh_globals *globals = __cxa_get_globals ();
return globals->uncaughtExceptions;
+#else
+ return 0;
+#endif
}
diff --git a/libstdc++-v3/libsupc++/eh_term_handler.cc b/libstdc++-v3/libsupc++/eh_term_handler.cc
index 46acee8..0d6ea2b 100644
--- a/libstdc++-v3/libsupc++/eh_term_handler.cc
+++ b/libstdc++-v3/libsupc++/eh_term_handler.cc
@@ -32,7 +32,7 @@
--disable-libstdcxx-verbose and rebuilding the library.
In a freestanding environment, we default to this latter approach. */
-#if _GLIBCXX_HOSTED && _GLIBCXX_VERBOSE
+#if _GLIBCXX_HOSTED && _GLIBCXX_VERBOSE && __cpp_exceptions
/* The current installed user handler. */
std::terminate_handler __cxxabiv1::__terminate_handler =
__gnu_cxx::__verbose_terminate_handler;