Re: [Mingw-users] problem when initializing a structure with a function marked as dllimport

[Danny S. <dan...@cl...>]

----- Original Message ----- 
From: "Vincent Torri" <vt...@un...>
To: <min...@li...>
Sent: Friday, April 24, 2009 5:58 AM
Subject: [Mingw-users] problem when initializing a structure with a function 
marked as dllimport


>
> Hey,
>
> when I compile the following sample code:
>
> 1) functs.h:
>
> void f(void *data);
> __declspec(dllimport) void g(void *data);
>
> 2) func_test.c:
>
> #include <stdlib.h>
> #include "funcs.h"
>
> typedef struct
> {
>   void (*func)(void *data);
>   void *data;
> } callback;
>
> typedef struct
> {
>   const char *name;
>   const callback cb[];
> } getopt;
>
> #define CB_FULL(fct, data) \
>   { fct, data }
>
> #define SENT { NULL, NULL }
>
> int main ()
> {
>   static const getopt c1 = { NULL, { CB_FULL( f, NULL), SENT } };
>   static const getopt c2 = { NULL, { CB_FULL( g, NULL), SENT } };
>
>   return 0;
> }
>
> with the following command:
>
> i586-mingw32msvc-gcc -c -o func_test func_test.c
>
> I have the following error:
>
> func_test2.c: In function 'main':
> func_test2.c:24: error: initializer element is not constant
> func_test2.c:24: error: (near initialization for 'c2.cb[0].func')
>
> so using a function which is not marked as dllimport (f), there is no
> problem, but with g, i have the error.
>
> I'm crosscompiling, but the real example (from which i create the sample
> code above) is also failing with mingw with the same error.
>
> Does someone know what the problem is, and how to solve it ?

Problem: dllimport'd symbols do not have a constant adddress at compile 
time.
How to solve: Upgrade to newer (4.2.x or later) gcc which ignores the 
dllimport on function whose address is used to initialize a variable

Here is the Changelog entry that fixed:

2007-03-29  Richard Henderson
 * varasm.c (initializer_constant_valid_p): Don't deny
 DECL_DLLIMPORT_P on functions.

 * config/i386/cygming.h: Remove function declarations.
 (SUBTARGET_ENCODE_SECTION_INFO): Don't undef first.
 (ASM_OUTPUT_LABELREF): Remove.
 (COMMON_ASM_OP): Remove.
 (ASM_OUTPUT_COMMON): Remove.
 (ASM_OUTPUT_ALIGNED_DECL_COMMON): New.
 (ASM_DECLARE_OBJECT_NAME): Use i386_pe_maybe_record_exported_symbol.
 (ASM_DECLARE_FUNCTION_NAME): Likewise.
 * config/i386/i386-interix.h (SUBTARGET_ENCODE_SECTION_INFO):
 Rename from TARGET_ENCODE_SECTION_INFO.
 * config/i386/netware.h: Likewise.
 * config/i386/i386-protos.h: Update.
 * config/i386/i386.c (ix86_function_ok_for_sibcall): Turn ifdef
 of TARGET_DLLIMPORT_DECL_ATTRIBUTES into straight if.
 (legitimate_constant_p): Reject dllimports.
 (dllimport_map, get_dllimport_decl): New.
 (legitimize_dllimport_symbol): New.
 (legitimize_address, ix86_expand_move): Use it.
 (TARGET_BINDS_LOCAL_P): Redefine for TARGET_DLLIMPORT_DECL_ATTRIBUTES.
 * config/i386/i386.h (DLL_IMPORT_EXPORT_PREFIX): Remove.
 (SYMBOL_FLAG_DLLIMPORT, SYMBOL_REF_DLLIMPORT_P): New.
 (SYMBOL_FLAG_DLLEXPORT, SYMBOL_REF_DLLEXPORT_P): New.
 * config/i386/predicates.md (constant_call_address_operand): Only
 accept symbols; reject dllimport_p symbols.
 * config/i386/uwin.h (ASM_DECLARE_FUNCTION_NAME): Use
 i386_pe_maybe_record_exported_symbol.
 * config/i386/winnt.c (DLL_IMPORT_PREFIX, DLL_EXPORT_PREFIX): Remove.
 (i386_pe_determine_dllexport_p): Rename from i386_pe_dllexport_p.
 (i386_pe_determine_dllimport_p): Rename from i386_pe_dllimport_p;
 trust the setting of DECL_DLLIMPORT_P.
 (i386_pe_dllexport_name_p, i386_pe_dllimport_name_p): Remove.
 (i386_pe_mark_dllexport, i386_pe_mark_dllimport): Remove.
 (gen_stdcall_or_fastcall_suffix): Return NULL if no change required;
 tidy the argument scanning loop.
 (i386_pe_encode_section_info): Set SYMBOL_FLAG_DLLIMPORT and
 SYMBOL_FLAG_DLLEXPORT in SYMBOL_REF_FLAGS.
 (i386_pe_strip_name_encoding): Remove.
 (i386_pe_binds_local_p): New.
 (i386_pe_strip_name_encoding_full): Use default_strip_name_encoding.
 (i386_pe_output_labelref): Remove.
 (i386_pe_asm_output_aligned_decl_common): New.
 (i386_pe_maybe_record_exported_symbol): Rename from
 i386_pe_record_exported_symbol; check for dllexported symbols.