Bug 1543 – std.boxer broken for gdc (was: Incorrect passing of floats to variadic functions)

The following program outputs 0 instead of the correct value (95): import std.stdio; import std.boxer; void main(char[][] args) { float a = 95.0f; Box b = box(a); writefln(b); } I have tested it with the latest svn version of gdc and it doesn't work rorrectly. It outputs the correct value when compiled with dmd.

The error seems to be from the fact that gdc doesn't pass correctly float arguments to variadic functions. In the following example the function foo_d() prints the expected value, but the function foo() doesn't. import std.stdio; void foo(...) { writefln(*cast(float*)_argptr); } void foo_d( ...) { writefln(*cast(double*)_argptr); } void main() { foo(10.1f); foo_d(10.1); }

Seems to be working here, if you avoid the unportable casts... import std.stdio; import std.stdarg; void foo(...) { writefln(va_arg!(float)(_argptr)); } void foo_d( ...) { writefln(va_arg!(double)(_argptr)); } void main() { foo(10.1f); foo_d(10.1); }

I didn't know about va_arg!()(). It seems then that std.boxer is broken for gdc, since it uses the unportable casts and assumes _argptr is of type void*, which by looking at std.stdarg it not necessarily true.

I think that's a known issue, since std.boxer says: "This module make not work on all GCC targets due to assumptions about the type of va_list."

Fixed this particular problem on targets for which std.boxer already works. Also fixed for 1- and 2-bit integral types. Fix is in SVN rev 183 / release 0.25.

sigh... make that svn rev 184