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Pointers to functions either not running or not linking

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Hi,

Trying to get pointers to functions working:


export function w $main() {
@body.1
    %.1 =l loadl $fred        # also tried  storel $fred, $pfred
    storel %.1, $pfred
    call $fred()
    call $pfred()             # <<<< fails here
    ret 0
}

function $fred() {
@body.1
    call $printf(l $str_hello)
    ret
}

data $pfred = {l 0}
data $str_hello = { b "hello\n", b 0 }


Compiles without linker error but I get a zsh: bus error  ./tmp2
when I run it. When I try taking the address of printf or fprintf
I get linker errors.

Solutions would be welcome or pointers on stuff to read up on too.

Thx,

-- David


PS

Linker errors are along the lines of:


final section layout:
    __TEXT/__text addr=0x100003EE8, size=0x000000D0, fileOffset=0x00003EE8, type=1
    __TEXT/__unwind_info addr=0x100003FB8, size=0x00000048, fileOffset=0x00003FB8, type=22
    __DATA/__data addr=0x100004000, size=0x0000001D, fileOffset=0x00004000, type=0
ld: ARM64 ADRP out of range (-4294979584 max is +/-4GB): from _main (0x100003EE8) to _printf@0x00000000 (0x00000000) in '_main' from /var/folders/_y/9km6chyj3mb5_ql1krwhcs4c0000gn/T/tmp-b3e919.o for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)


But my Google and chatGPT foo are failing to help me diagnose at the moment.
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On Tue May 9, 2023 at 2:46 PM CEST, dangermouseb wrote:
> export function w $main() {
> @body.1
>     %.1 =l loadl $fred        # also tried  storel $fred, $pfred

%.1 =l copy $fred
call %.1()

something like this is what you need.
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Your IL file is very wrong. Here is something that
has a chance to work:

export function w $main() {
@body.1
    storel $fred, $pfred  # stores the address of the fred function
                          # into the global pfred
    %fn =l loadl $pfred   # loads an address from the global pfred
    call %fn()            #   calls this address
    ret 0
}

function $fred() {
@body.1
    call $printf(l $str_hello, ...)
    ret
}

data $pfred = {l 0}
data $str_hello = { b "hello\n", b 0 }
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> %.1 =l copy $fred
> call %.1()
> 
> something like this is what you need.

Brilliant - that worked nicely. Thank you.

My next question is how to get hold of stderr so I can use fprintf.
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On Tue, May 9, 2023, at 14:51, Drew DeVault wrote:
> %.1 =l copy $fred
> call %.1()

Note that qbe will hastily get rid of the copy and
just turn this code into:

   call $fred()
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On Tue May 9, 2023 at 3:02 PM CEST, Quentin Carbonneaux wrote:
> Note that qbe will hastily get rid of the copy and
> just turn this code into:
>
>    call $fred()

'course :)
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Quoth dangermouseb <dangermouseb@forwarding.cc>:
> 
> > %.1 =l copy $fred
> > call %.1()
> > 
> > something like this is what you need.
> 
> Brilliant - that worked nicely. Thank you.
> 
> My next question is how to get hold of stderr so I can use fprintf.
> 
> 
> 

that depends very heavily on your libc; you'll have to
read the headers and see how it's defined. eg, on OpenBSD:

	#define stdin (&__sF[0])

on other systems it will be different.
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>> 
>> My next question is how to get hold of stderr so I can use fprintf.
>> 
> 
> that depends very heavily on your libc; you'll have to
> read the headers and see how it's defined. eg, on OpenBSD:
> 
> #define stdin (&__sF[0])
> 
> on other systems it will be different.
> 


So I lifted `extern FILE *__stderrp` from stdio.h, assumed it was
void * in QBE, but could figure out the link problem for macOS.




#define stderr __stderrp

where

extern FILE *__stderrp;

typedef struct __sFILE {
    ...
} FILE;

int fprintf(FILE * restrict, const char * restrict, ...) __attribute__((__format__ (__printf__, 2, 3)));



What seems odd is I can link printf okay.
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On Tue, May 9, 2023, at 15:49, dangermouseb wrote:
> So I lifted `extern FILE *__stderrp` from stdio.h, assumed it was
> void * in QBE, but could figure out the link problem for macOS.

See my answer to your other mail. qbe does not do well
with taking the address of dynamically-linked symbols.
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