Need help adding an error to gcc (C++)

[Craig Rodrigues]

Hi,

I am looking at PR 4926:

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&database=gcc&pr=4926


The following C++ testcase will crash the compiler:


====================================================================
namespace ExprType
{
    struct UnknownType;

    template<unsigned>
    struct ETType
    {
        typedef UnknownType Type;
    };


    template<typename T>
    struct ETArray
    {
        char array[1];
    };


    template<typename T>
    ETArray<T> etFunc(const T& t);
}

    namespace ExprType{ template<> struct ETArray<int > { char array[7]; }; template<> struct ETType<7> { typedef int Type; };}
    namespace ExprType{ template<> struct ETArray<double > { char array[12]; }; template<> struct ETType<12> { typedef double Type; };}

struct F
{
    int operator()(int,double) const
    {
        return 3;
    }
} f;

template<typename T>
T makeT();

template<typename Func,typename Arg1,typename Arg2>
typename ExprType::ETType<sizeof(ExprType::etFunc(makeT<Func>()(makeT<Arg1>(),makeT<Arg2>())).array)>::Type doCall(const Func& func,const Arg1& a1,const Arg2& a2)
{
    return func(a1,a2);
}


int main()
{
    doCall(f,4,7.5);
}

====================================================================

The backtrace of the problem leads to:

#0  0x400a5f27 in strlen (str=0x0) at ../sysdeps/i386/strlen.c:28
#1  0x0811b7bc in write_expression (expr=0x401855f0)
    at cp/mangle.c:1830
#2  0x0811b881 in write_expression (expr=0x40186140)
    at cp/mangle.c:1856
#3  0x0811b881 in write_expression (expr=0x40186160)
    at cp/mangle.c:1856
#4  0x0811b881 in write_expression (expr=0x40185618)
    at cp/mangle.c:1856
#5  0x0811c79d in write_template_arg (node=0x40185618)
    at cp/mangle.c:1967
#6  0x0811b668 in write_template_args (args=0x40185640)


I am playing around with a patch:


Index: mangle.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cp/mangle.c,v
retrieving revision 1.44
diff -u -r1.44 mangle.c
--- mangle.c	2002/02/20 04:09:04	1.44
+++ mangle.c	2002/03/07 05:05:08
@@ -1825,7 +1825,13 @@
 
 	  code = TREE_CODE (expr);
 	}
-      
+
+      if (! operator_name_info[(int) code].mangled_name )
+        { 
+          error ("Error during template instantiation");
+	  return;
+	}
+
       /* If it wasn't any of those, recursively expand the expression.  */
       write_string (operator_name_info[(int) code].mangled_name);
 


This seems to prevent the compiler crash, but
I am not familiar enough with gcc to know what to put
for the error message.

Can someone help me with this?

Thanks.
-- 
Craig Rodrigues        
http://www.gis.net/~craigr    
rodrigc@attbi.com