sf.net # 997: gcc backend: handle EXTERN "rtlib"

- preserve the internally mangled name
- emit an extra prototype to map the internal name to the external ASM name
- previously extern "rtlib" and -gen gcc backend was causing a duplicated
  definition because the defined name was global completely disregarding
  the namespace
- the intent is that the namespace is preserved internally and mapped
  to an external c procedure (i.e. more than one name can alias an existing
  procedure)

changelog.txt

@@ -33,6 +33,7 @@ Version 1.20.0
 - gas64: NEW UBYTE/BYTE[count] not handled (SARG)
 - sf.net #988: (regression) re-allow overloaded non-indexed array arguments - Can't pass UDT member array to an overloaded sub
 - gas64: 'SI' word found in cvtsi2ss wrongly releasing RSI register (SARG)
+- sf.net #997: gcc backend: handle EXTERN "rtlib": preserve the internally mangled name but emit an extra prototype to map the internal name to the external ASM name
 
 
 Version 1.10.1

src/compiler/ir-hlc.bas

@@ -467,7 +467,13 @@ private function hGetMangledNameForASM _
 
 	dim as string mangled
 
-	mangled = *symbGetMangledName( sym )
+	'' rtlib mangling?  Just use the alias if one was given
+	if( (symbGetMangling( sym ) = FB_MANGLING_RTLIB) andalso _
+	    (sym->id.alias <> NULL) ) then
+		mangled = *sym->id.alias
+	else
+		mangled = *symbGetMangledName( sym )
+	end if
 
 	if( underscore_prefix and env.underscoreprefix ) then
 		mangled  = "_" + mangled
@@ -487,6 +493,12 @@ end function
 private function hNeedAlias( byval proc as FBSYMBOL ptr ) as integer
 	function = FALSE
 
+	'' rtlib mangling?  Expect we always need the asm alias
+	if( symbGetMangling( proc ) = FB_MANGLING_RTLIB ) then
+		function = TRUE
+		exit function
+	end if 
+
 	'' Only on systems where gcc would use the @N suffix
 	if( fbGetCpuFamily( ) <> FB_CPUFAMILY_X86 ) then
 		exit function

src/compiler/symb-mangling.bas

@@ -668,7 +668,9 @@ private function hDoCppMangling( byval sym as FBSYMBOL ptr ) as integer
 	end if
 
 	'' extern "rtlib"? disable cpp mangling
-	if( symbGetMangling( sym ) = FB_MANGLING_RTLIB ) then
+	if( (symbGetMangling( sym ) = FB_MANGLING_RTLIB) _
+	    andalso (env.clopt.backend <> FB_BACKEND_GCC) _
+	    andalso (sym->id.alias <> NULL) ) then
 		'' disable cpp mangling only if it's not internally generated:
 		'' Internally generated symbols:
 		''   - vtable