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User-Agent: Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)

Description of problem:
typedef struct
{
    struct {
        union {
            double d;
        } x;
    } x;
} S2;


__attribute__((regparm(3))) void f2(S2);

In gcc version 2.96, the parameter to f2 is passed on the stack.  In version 
3.0.3, the parameter is passed in 2 registers, eax and edx.

This can cause binaries compiled with 2.96 to not be interoperable with 
binaries compiled with 3.0.3.


Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1.gcc -c try1.c      # Use gcc version 2.96
2.gcc try2.c try1.o  # Use gcc version 3.0.3
3.a.out

Note that the problem also happens if you compile try1.c with 3.0.3 and compile 
try2.c with 2.96.  Also, it's pretty easy to see this problem if you just 
produce the assembly files with the two compilers.


Actual Results:  a.out outputs the following:

s.x.x.d = -1.997456; it should be 5.0


Expected Results:  s.x.x.d = 5.000000; it should be 5.0


Additional info: