http://d.puremagic.com/issues/show_bug.cgi?id=5069

           Summary: No missing extern(C) error
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: accepts-invalid, diagnostic
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2010-10-17 05:21:22 PDT ---
This is a wrong D2 program:


import std.c.stdlib: qsort;
import std.c.stdio: printf;

int compare(const void *a, const void *b) {
    return *cast(int*)a - *cast(int*)b;
}

void main () {
    int[] values = [40, 10, 100, 90, 20, 25];

    for (int n = 0; n < 6; n++)
        printf ("%d ", values[n]);
    printf("\n");

    qsort(values.ptr, 6, int.sizeof, &compare);

    for (int n = 0; n < 6; n++)
        printf ("%d ", values[n]);
    printf("\n");
}


With DMD 2.049 it compiles with no errors, and then sefaults at runtime.

To fix it the compare() must have a C calling convention:

extern(C) int compare(const void *a, const void *b) {


DMD 1.026 avoids that runtime error with a useful compile-time error message that I'd like in DMD2 too:

Line 15: function std.c.stdlib.qsort (void*,uint,uint,int(C *)(void*, void*))
does not match parameter types (int*,int,uint,int(*)(void*, void*))
Line 15: Error: cannot implicitly convert expression (& compare) of type
int(*)(void*, void*) to int(C *)(void*, void*)


A better single error message for D2 may say "extern(C)" too somewhere in the
error message, instead of just saying a less clear "expression (& compare) of
type int(*)(void*, void*) to int(C *)(void*, void*)". Something like:

Line 15: Error: cannot implicitly convert expression (& compare) of type int
function(const void*, const void*) to extern(C) int function(const void*, const
void*)

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yebblies <yebblies@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yebblies@gmail.com


--- Comment #1 from yebblies <yebblies@gmail.com> 2010-10-17 06:59:01 PDT ---
Related to http://d.puremagic.com/issues/show_bug.cgi?id=3797

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Sobirari Muhomori <dfj1esp02@sneakemail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE


--- Comment #2 from Sobirari Muhomori <dfj1esp02@sneakemail.com> 2010-10-18 10:58:09 PDT ---
*** This issue has been marked as a duplicate of issue 3797 ***

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--- Comment #3 from bearophile_hugs@eml.cc 2011-09-02 04:01:25 PDT ---
With this fix: https://github.com/D-Programming-Language/dmd/commit/306df8eaa6f8a987f76f401a1e03d8edf1f1e2ae

Now DMD prints:

test.d(15): Error: function core.stdc.stdlib.qsort (void* base, uint nmemb,
uint size, int C function(in const(void*), in const(void*)) compar) is not
callable using argument types (int*,int,uint,int function(in const(void*), in
const(void*)))
test.d(15): Error: cannot implicitly convert expression (& compare) of type int
function(in const(void*), in const(void*)) to int C function(in const(void*),
in const(void*))


Instead of:
int C function(in const(void*), in const(void*))

I think this allows to see the C better:
int extern(C) function(in const(void*), in const(void*))

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--- Comment #4 from yebblies <yebblies@gmail.com> 2011-09-02 23:15:22 EST ---
(In reply to comment #3)
> With this fix: https://github.com/D-Programming-Language/dmd/commit/306df8eaa6f8a987f76f401a1e03d8edf1f1e2ae
> 
> Now DMD prints:
> 
> test.d(15): Error: function core.stdc.stdlib.qsort (void* base, uint nmemb,
> uint size, int C function(in const(void*), in const(void*)) compar) is not
> callable using argument types (int*,int,uint,int function(in const(void*), in
> const(void*)))
> test.d(15): Error: cannot implicitly convert expression (& compare) of type int
> function(in const(void*), in const(void*)) to int C function(in const(void*),
> in const(void*))
> 
> 
> Instead of:
> int C function(in const(void*), in const(void*))
> 
> I think this allows to see the C better:
> int extern(C) function(in const(void*), in const(void*))

I agree.  Is there an enhancement request already open for this?

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--- Comment #5 from bearophile_hugs@eml.cc 2011-09-02 10:13:59 PDT ---
(In reply to comment #4)

> I agree.  Is there an enhancement request already open for this?

bug 6596

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