Comment #0 by default_357-line — 2007-01-06T19:38:25Z
http://paste.dprogramming.com/dpdd066k.php
When putting inout real parameters directly on the floating point stack, doing stuff and popping them back, for some reason the parameter doesn't get changed. Verified on win32/mingw-gdc0.21svn and linux/dmd1.0
Update (5 minutes later)
This is beyond odd. I've got an inout variable changing addresses.
Replace the test function in the paste with
void test(inout real r) {
version(Tango) (new DisplayWriter(Cout))("Before: r is "c)(cast(int)cast(void*)&r)("\n"c)();
else writefln("Before: r is ")(cast(void*)(&r));
asm { fld r; fsin; fstp r; }
version(Tango) (new DisplayWriter(Cout))("After: r is "c)(cast(int)cast(void*)&r)("\n"c)();
else writefln("After: r is ")(cast(void*)(&r));
}
I got the following output: "Before: r is <someaddress>" "After: r is 0"
Please enlighten me.
Greetings
Comment #1 by bugzilla — 2007-02-02T03:16:25Z
inout parameters are passed by reference, i.e. they are actually a pointer. The sample code is using inline assembler, referencing the inout parameter. So, the inline assembler:
void foo(inout real r)
{
asm
{ fld r;
is actually loading a *pointer* and treating it as if it were a real.
Inline assembler does exactly what you tell it to do. To make the above work, use instead:
mov EAX,r ;
fld real ptr [EAX] ;
Not a compiler bug.