http://bugzilla.gdcproject.org/show_bug.cgi?id=226
Iain Buclaw <ibuc...@gdcproject.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |INVALID
Status|NEW |RESOLVED
--- Comment #1 from Iain Buclaw <ibuc...@gdcproject.org> ---
bug226.c
---
#include <stdio.h>
#define MAX(a,b) (((a)>(b))?(a):(b))
typedef unsigned long long ulong;
typedef union Foo
{
double a;
ulong b;
} Foo;
int main()
{
printf("%d >= %d\n%d >= %d\n",
sizeof(Foo), MAX(sizeof(double), sizeof(ulong)),
__alignof__(Foo), MAX(__alignof__(double), __alignof__(ulong)));
}
---
bug226.cc
---
#include <iostream>
#include <algorithm>
union Foo
{
double a;
ulong b;
};
int main()
{
std::cout << sizeof(Foo) << " >= "
<< std::max(sizeof(double), sizeof(ulong)) << "\n";
std::cout << alignof(Foo) << " >= "
<< std::max(alignof(double), alignof(ulong)) << "\n";
}
---
bug226.d
---
import std.stdio;
import std.algorithm;
union Foo
{
double a;
ulong b;
}
void main()
{
writeln(Foo.sizeof, " >= ", max(double.sizeof, ulong.sizeof));
writeln(Foo.alignof, " >= ", max(double.alignof, ulong.alignof));
}
---
$ gcc -m32 bug226.c -o gccm32
$ g++ -m32 bug226.cc -o gxxm32
$ gdc -m32 bug226.d -o gdcm32
$ ./gccm32
8 >= 8
4 >= 8
$ ./gxxm32
8 >= 8
4 >= 8
$ ./gdcm32
8 >= 8
4 >= 8
---
GDC may be different from other D compilers, but it stays true to ABI of C and
C++ here, so what do you expect me to do? Everyone else is in the wrong here.
The alignment of double and ulong on x86 may be 8 bytes, but the field
alignment is worked out differently.
---
version (X86_64)
return T.alignof;
else version (X86)
{
static if (isIntegral(T) || is(T == double) || is(T == cdouble))
return min(4, T.alignof);
else
return T.alignof;
}
---
The above is roughly what LDC and DMD should be doing.
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