Support weak references (#28)

The patch adds support for weak references. The original MinGW implementation targets ix86, which handles weak symbols differently compared to AArch64. In AArch64, the weak symbols are replaced in all places, leading to missing declarations.

Author: eukarpov

gcc/config/aarch64/cygming.h

@@ -279,7 +279,7 @@ extern void i386_pe_record_external_function (tree, const char *);
     mingw_handle_selectany_attribute, NULL }
 
 #undef SUB_TARGET_RECORD_STUB
-#define SUB_TARGET_RECORD_STUB mingw_pe_record_stub
+#define SUB_TARGET_RECORD_STUB(NAME, DECL) mingw_pe_record_stub((NAME), DECL_WEAK((DECL)))
 
 #define SUPPORTS_ONE_ONLY 1
 
@@ -314,7 +314,8 @@ do {							\
 #undef GOT_ALIAS_SET
 #define GOT_ALIAS_SET mingw_GOT_alias_set ()
 
-#define PE_COFF_LEGITIMIZE_EXTERN_DECL 0
+#define PE_COFF_LEGITIMIZE_EXTERN_DECL(RTX) \
+  (GET_CODE (RTX) == SYMBOL_REF && SYMBOL_REF_WEAK(RTX))
 
 #define HAVE_64BIT_POINTERS 1
 

gcc/config/i386/cygming.h

@@ -461,7 +461,7 @@ do {						\
 #define TARGET_ASM_ASSEMBLE_VISIBILITY i386_pe_assemble_visibility
 
 #undef SUB_TARGET_RECORD_STUB
-#define SUB_TARGET_RECORD_STUB mingw_pe_record_stub
+#define SUB_TARGET_RECORD_STUB(NAME, DECL) mingw_pe_record_stub((NAME), 0)
 
 /* Static stack checking is supported by means of probes.  */
 #define STACK_CHECK_STATIC_BUILTIN 1
@@ -470,7 +470,7 @@ do {						\
 # define HAVE_GAS_ALIGNED_COMM 0
 #endif
 
-#define PE_COFF_LEGITIMIZE_EXTERN_DECL \
+#define PE_COFF_LEGITIMIZE_EXTERN_DECL(RTX) \
   (ix86_cmodel == CM_LARGE_PIC || ix86_cmodel == CM_MEDIUM_PIC)
 
 #define HAVE_64BIT_POINTERS TARGET_64BIT_DEFAULT

gcc/config/mingw/winnt-dll.cc

@@ -134,7 +134,7 @@ get_dllimport_decl (tree decl, bool beimport)
     {
       SYMBOL_REF_FLAGS (rtl) |= SYMBOL_FLAG_EXTERNAL;
 #ifdef SUB_TARGET_RECORD_STUB
-      SUB_TARGET_RECORD_STUB (name);
+      SUB_TARGET_RECORD_STUB (name, decl);
 #endif
     }
 
@@ -206,7 +206,7 @@ legitimize_pe_coff_symbol (rtx addr, bool inreg)
 	}
     }
 
-  if (!PE_COFF_LEGITIMIZE_EXTERN_DECL)
+  if (!PE_COFF_LEGITIMIZE_EXTERN_DECL(addr))
     return NULL_RTX;
 
   if (GET_CODE (addr) == SYMBOL_REF

gcc/config/mingw/winnt.cc

@@ -635,6 +635,7 @@ struct GTY(()) stub_list
 {
   struct stub_list *next;
   const char *name;
+  bool is_weak_decl_needed;
 };
 
 static GTY(()) struct export_list *export_head;
@@ -672,7 +673,7 @@ mingw_pe_maybe_record_exported_symbol (tree decl, const char *name, int is_data)
 }
 
 void
-mingw_pe_record_stub (const char *name)
+mingw_pe_record_stub (const char *name, bool is_weak_decl_needed)
 {
   struct stub_list *p;
 
@@ -691,6 +692,7 @@ mingw_pe_record_stub (const char *name)
   p = ggc_alloc<stub_list> ();
   p->next = stub_head;
   p->name = name;
+  p->is_weak_decl_needed = is_weak_decl_needed;
   stub_head = p;
 }
 
@@ -807,6 +809,15 @@ mingw_pe_file_end (void)
 	  if (!startswith (name, "refptr."))
 	    continue;
 	  name += 7;
+
+	  if (q->is_weak_decl_needed)
+	    {
+#ifdef ASM_WEAKEN_LABEL
+        ASM_WEAKEN_LABEL (asm_out_file, name);
+#endif
+        mingw_pe_declare_function_type(asm_out_file, name, 1);
+	    }
+
 	  fprintf (asm_out_file, "\t.section\t.rdata$%s, \"dr\"\n"
 	  		   "\t.globl\t%s\n"
 			   "\t.linkonce\tdiscard\n", oname, oname);

gcc/config/mingw/winnt.h

@@ -30,7 +30,7 @@ extern void mingw_pe_declare_function_type (FILE *file, const char *name,
 extern void mingw_pe_encode_section_info (tree, rtx, int);
 extern void mingw_pe_file_end (void);
 extern void mingw_pe_maybe_record_exported_symbol (tree, const char *, int);
-extern void mingw_pe_record_stub (const char *);
+extern void mingw_pe_record_stub (const char *, bool);
 extern unsigned int mingw_pe_section_type_flags (tree, const char *, int);
 extern void mingw_pe_unique_section (tree, int);
 extern bool mingw_pe_valid_dllimport_attribute_p (const_tree);