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Re: [PATCH] libstdc++: Fix exceptions being generated when compiling with -fno-exceptions


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;

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