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digitalmars.D.bugs - [Issue 5815] New: Using -O is causing wrong code to be generated for extern(C) method call.

reply d-bugmail puremagic.com writes:
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           Summary: Using -O is causing wrong code to be generated for
                    extern(C) method call.
           Product: D
           Version: unspecified
          Platform: x86_64
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: opantm+spam gmail.com


--- Comment #0 from opantm+spam gmail.com 2011-04-06 10:55:30 PDT ---
When attempting to call a Windows API function, PathRemoveFileSpecA, invalid
results are returned when using the -O compiler flag. When using the same file,
but without -O, the correct output is generated.

Test Case:

import std.stdio;
import std.c.windows.windows;        

static const ushort MAX_PATH = 260;    
extern(C) BOOL PathRemoveFileSpecA(LPTSTR);    

static void TrimToNull(ref char[] String) {
    for(int i = 0; i < String.length; i++)
        if(String[i] == '\0') {
            String = String[0..i];    
            return;
        }
}

static char[] GetDirectoryPath(string FilePath) {            
    char[] Copy = FilePath.dup;    
    uint Result = PathRemoveFileSpecA(Copy.ptr);
    TrimToNull(Copy);
    return Copy;
}

int main(string[] args) {
    string Path = "D:\\Test Path\\Test.exe";
    auto Dir = GetDirectoryPath(Path);
    writefln("Dir: " ~ Dir);    
    return 0;
}


Output without -O: "Dir: D:\Test Path"
Output with -O: "object.Error: Access Violation"

For this particular example, shlwapi.lib must be generated with Implib.exe and
linked. 

The version of DMD being used is 2.052. OS is Windows, and compiled with: "dmd
testfile.d shlwapi.lib (-O)".

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Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla digitalmars.com
           Platform|x86_64                      |x86


--- Comment #1 from Walter Bright <bugzilla digitalmars.com> 2011-04-06
13:11:33 PDT ---
x86_64 (i.e. 64 bit code) is not currently supported by DMD on Windows.
Changing to x86.

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Rainer Schuetze <r.sagitario gmx.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |r.sagitario gmx.de


--- Comment #2 from Rainer Schuetze <r.sagitario gmx.de> 2011-04-06 14:09:38
PDT ---

 extern(C) BOOL PathRemoveFileSpecA(LPTSTR);


You are probably using the wrong calling convention here, it should be
"extern(Windows)", which corresponds to __stdcall in while "extern(C)" is
__cdecl in the SDK C++ headers.

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--- Comment #3 from opantm+spam gmail.com 2011-04-08 19:29:19 PDT ---
(In reply to comment #1)

 x86_64 (i.e. 64 bit code) is not currently supported by DMD on Windows.
 Changing to x86.


Sorry, I did mean x86.

(In reply to comment #2)

 extern(C) BOOL PathRemoveFileSpecA(LPTSTR);


 
 You are probably using the wrong calling convention here, it should be
 "extern(Windows)", which corresponds to __stdcall in while "extern(C)" is
 __cdecl in the SDK C++ headers.


As far as I can tell, the calling convention is C. According to MSDN, the
header is "BOOL PathRemoveFileSpec(__inout  LPTSTR pszPath)". As a comparison,
GetCurrentDirectory (which uses extern(Windows)) is "DWORD WINAPI
GetCurrentDirectory(__in   DWORD nBufferLength, __out  LPTSTR lpBuffer)". When
using extern(Windows), it fails to compile due to an undefined symbol error.

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--- Comment #4 from Rainer Schuetze <r.sagitario gmx.de> 2011-04-08 23:22:01
PDT ---
If you look it up in shlwapi.h in the SDK, it is declared as

LWSTDAPI_(BOOL)     PathRemoveFileSpecA(__inout LPSTR pszPath);

and LWSTDAPI_(BOOL) expands to 'extern "C" __declspec(dllimport) BOOL
__stdcall'.
__stdcall translates to D as extern(Windows).

I have tried your code, and I get a link error with "extern(C)". I have used
coff2implib to convert the library from the sdk, because I have had problems
with implib on DLLs in the past, it especially misses a number of symbols.

With "extern(Windows)", I can link and run your code without problems.

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--- Comment #5 from Rainer Schuetze <r.sagitario gmx.de> 2011-04-08 23:23:56
PDT ---

 I have used coff2implib


sorry, it is called coffimplib and available from the digitalmars ftp area.

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opantm+spam gmail.com changed:

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


--- Comment #6 from opantm+spam gmail.com 2011-04-09 10:27:41 PDT ---
(In reply to comment #4)

 If you look it up in shlwapi.h in the SDK, it is declared as
 
 LWSTDAPI_(BOOL)     PathRemoveFileSpecA(__inout LPSTR pszPath);
 
 and LWSTDAPI_(BOOL) expands to 'extern "C" __declspec(dllimport) BOOL
 __stdcall'.
 __stdcall translates to D as extern(Windows).
 
 I have tried your code, and I get a link error with "extern(C)". I have used
 coff2implib to convert the library from the sdk, because I have had problems
 with implib on DLLs in the past, it especially misses a number of symbols.
 
 With "extern(Windows)", I can link and run your code without problems.


Awesome. After getting coffimplib and converting with it instead as well as
changing to extern(Windows), it works both with and without -O. :) Thanks for
the help. I guess this bug report is invalid.

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