[Bug c/15883] New: allow mixed regparm / standard calling convention

[avi at exanet dot com]

Currently, the only way to safely use regparm is to compile everything (system 
libraries, third party libraries, and the application) with it. This is usually 
only possible for completely self-contained projects, such as the Linux kernel. 
 
While it is possible to specify that a particular function uses the regparm 
calling convention, via __attribute__((regparm)), it is impossible to do so 
safely: 
 
- (C, C++) gcc silently converts a regparm function to a non-regparm function 
pointer: 
 
__attribute__((regparm(3))) 
int f(int x) { return x+1; } 
 
int (*p)(int x) = f; // ERROR 
 
- (C++) g++ allows an overriding virtual function to have a different calling 
convention that the overridden function: 
 
struct C { 
    __attribute__((regparm(3))) 
	virtual int f(int x) { return x+1; } 
}; 
 
struct D : C { 
	virtual int f(int x) { return x+2; } // ERROR 
}; 
 
 
 
The calling convention should be treated similarly to 'const'. Conversion from 
one convention to the other should be flagged as an error. 
 
Other features that would improve regparm usability: 
 
- a pragma to set calling convention for an entire header 
- allow setting the calling convention for a C++ class, setting the default for 
all its members.

-- 
           Summary: allow mixed regparm / standard calling convention
           Product: gcc
           Version: 3.3.3
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: avi at exanet dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-redhat-linux
  GCC host triplet: i386-redhat-linux
GCC target triplet: i386-redhat-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15883