exceptions and optimization

[Alex Achenbach <achenbac at stud dot uni-frankfurt dot de>]

I don't know whether this has come up yet, but there's a bug in
support for exceptions in egcs 1.0.3a when any optimization (-O#)
is turned on for a source module containing functions that a
stack frame unwind path leads through (but that do not actually
catch/check exceptions themselves).

The following code (two modules) triggers the bug:

--- x.cc ------------------------------------------------
#include <iostream>
void foo();			// potential thrower
int main() {
    try {
    	foo();
    }
    catch (int) { cout << "gotcha" << endl; }
    return 0;
}
--- y.cc ------------------------------------------------
#include <iostream>
void foo() {
    throw 4;	// will segfault if -O1, -O2, or -O3
}
---------------------------------------------------------
(eg compiled as     g++ -O2 x.cc y.cc -o xy   )

In y.cc::foo(), the throw will segfault. The reason seems to be
that optimization removes the exception table of any function
that does not itself catch/check exceptions (just a guess).
The problem does not occur if either foo() is defined as
	
	void foo() throw (int) { /* ... */ }

in y.cc, or is changed to

	void foo() {
	    try {
		throw 4;
	    }
	    catch (...) {
		throw;
	    }
	}

Cheers,

Alex

-- 
_____________________________________________________________________

   Alexander Achenbach              achenbac@stud.uni-frankfurt.de
_____________________________________________________________________