Should betterC modules and programs be able to use the modules under core.stdc? I certainly expected they should, or at least for many modules.

The specific issue I ran in to was with varargs routines, and making use of core.stdc.stdarg, where I had to link with phobos.

$ cat stdarg1.d
import core.stdc.stdarg;

pragma(printf)
public extern(C) int wrap_printf(scope const char* f, ...) {
	import core.stdc.stdio;

	va_list ap;

	va_start(ap, f);
	auto rc = vprintf(f, ap);
	va_end(ap);

	return rc;
}

extern(C) void main() {
	wrap_printf("Foo\n");
}

$ dmd -betterC stdarg1.d
/usr/bin/ld: stdarg1.o: in function `wrap_printf':
stdarg1.d:(.text.wrap_printf[wrap_printf]+0xce): undefined reference to `_D4core4stdc6stdarg6va_endFNbNiPSQBf8internal6vararg8sysv_x6413__va_list_tagZv'
collect2: error: ld returned 1 exit status
Error: undefined reference to `nothrow @nogc void core.stdc.stdarg.va_end(core.internal.vararg.sysv_x64.__va_list_tag*)`
       referenced from `wrap_printf`
       perhaps `.d` files need to be added on the command line, or use `-i` to compile imports
Error: linker exited with status 1
       cc stdarg1.o -o stdarg1 -m64 -Xlinker --export-dynamic -L/usr/lib/x86_64-linux-gnu -lpthread -lm -lrt -ldl

Yet I can make it link, and work using:

$ dmd -c -betterC stdarg1.d
$ dmd -of=stdarg1 stdarg1.o
$ ./stdarg1
Foo

I tried to work around this via the following, and various variations, however I ran a different issue.

$ cat stdarg2.d
pragma(printf)
public extern(C) int wrap_printf(scope const char* f, ...) {
	import stdarg2c;
	extern(C) int vprintf(scope const char*, va_list);

	va_list ap;

	va_start(ap, f);
	auto rc = vprintf(f, ap);
	va_end(ap);

	return rc;
}

extern(C) void main() {
	wrap_printf("Foo2\n");
}
$ cat stdarg2c.c
#include <stdarg.h>

$ dmd -betterC stdarg2.d
stdarg2.d(2): Error: `__va_list_tag` is not defined, perhaps `import core.stdc.stdarg;` ?

Actually importing core.stdc.stdarg as it suggests simply brings back the original issue.

On Thursday, 10 October 2024 at 20:48:45 UTC, Derek Fawcus wrote:

Should? yes
Will? unlikely

BetterC and the platforms it enables should not be considered supported

import core.stdc.stdarg;


// add this
extern(C) void va_end(void* ap){}

pragma(printf)
public extern(C) int wrap_printf(scope const char* f, ...) {
    import core.stdc.stdio;

    va_list ap;

    va_start(ap, f);
    auto rc = vprintf(f, ap);
    va_end(ap);

    return rc;
}


extern(C) void main(int argc, const(char)** argv)
{
    wrap_printf("Foo\n");
}

Adding: extern(C) void va_end(void* ap){} works for me, looks like DMD doesn't do its job properly

If -betterC can't do what C does, then it's not -betterC, but -worseC

To me this is a bug and it should be reported

On Friday, 11 October 2024 at 05:39:06 UTC, ryuukk_ wrote:

Thanks for the suggestions folks, so I've created a bug ticket, and attached a diff to fix the issue. It did however reveal another similar issue with lack of access to alloca() from betterC.

https://issues.dlang.org/show_bug.cgi?id=24814

On Monday, 14 October 2024 at 20:32:08 UTC, Derek Fawcus wrote:

That alloca issue is:

https://issues.dlang.org/show_bug.cgi?id=24815