int decl_interposable(decl *d)
{
/*
* Match gcc's -fsemantic-interposition default, where:
*
* -fpic -fpie -fsemantic-interposition function-visibility | can-inline-non-static function?
* 0 0 0 default yes (-fno-pic)
* 0 0 1 default yes (-fno-pic)
* 0 1 0 default yes (-fno-pic)
* 0 1 1 default yes (-fno-pic)
* 0 0 0 protected/hidden yes (-fno-pic)
* 0 0 1 protected/hidden yes (-fno-pic)
* 0 1 0 protected/hidden yes (-fno-pic)
* 0 1 1 protected/hidden yes (-fno-pic)
*
* 1 1 1 protected/hidden yes (-fvisibility=protected/hidden)
* 1 1 0 protected/hidden yes (-fvisibility=protected/hidden)
* 1 0 1 protected/hidden yes (-fvisibility=protected/hidden)
* 1 0 0 protected/hidden yes (-fvisibility=protected/hidden)
*
* 1 1 1 default yes (-fpie)
* 1 1 0 default yes (-fpie)
* 1 0 1 default no
* 1 0 0 default yes (-fno-semantic-interposition)
*
* -fno-pic: -fsemantic-interposition and -fvisibility=... have no effect
*
* -fpic: We can inline non-static, default-visibility functions when
* -fno-semantic-interposition is set otherwise, the ELF abi says a
* non-static default-visibility function may be overridden.
*/
if(!cc1_fopt.pic && !cc1_fopt.pie)
return 0; /* not compiling for interposable shared library */
if(cc1_fopt.pie && decl_defined(d, 0))
return 0; /* pie, this is the main program, can't have its symbols interposed */
switch(decl_linkage(d)){
case linkage_internal:
case linkage_none:
return 0; /* static decl, fixed */
case linkage_external:
break;
}
switch(decl_visibility(d)){
case VISIBILITY_DEFAULT:
break;
case VISIBILITY_PROTECTED:
return 0; /* symbol visible, but not interposable by contract */
case VISIBILITY_HIDDEN:
return 0; /* symbol not visible, so not interposable */
}
/* extern decls (that aren't explicitly visibility-attributed) are interposable */
if(!decl_defined(d, 0))
return 1;
return cc1_fopt.semantic_interposition;
}
int decl_needs_GOTPLT(decl *d)
{
/* need to differentiate:
* extern int x; // always pic (aka x@GOTPCREL(%rip))
*
* __attribute__((visibility("hidden/protected")))
* extern int x; // pic but we can avoid the GOT, e.g. x(%rip)
*
* int x = 3; // pic, must go via GOT
*
* -fno-semantic-interposition / -fpie
* int x = 3; // pic, can avoid the GOT because it's effectively hidden/protected
*
* -fno-semantic-interposition / -fno-pie (but -fpic)
* extern int x; // pic, must use GOT as we don't know if it's in our module
*/
if(!cc1_fopt.pic && !cc1_fopt.pie)
return 0;
if(decl_linkage(d) == linkage_internal)
return 0;
if(cc1_fopt.pie){
/* gcc acts as if variables are always local/accessible without the GOT in pie-code */
int is_var = 0; /* !type_is(d->ref, type_func) */
if((is_var || decl_defined(d, 0)) && !attribute_present(d, attr_weak))
return 0;
}
switch(decl_visibility(d)){
case VISIBILITY_DEFAULT:
break;
case VISIBILITY_HIDDEN:
case VISIBILITY_PROTECTED:
return 0;
}
return 1;
}
void asm_declare_decl_init(decl *d)
{
enum section_type sec;
if((d->store & STORE_MASK_STORE) == store_extern){
asm_predeclare_extern(d);
return;
}
sec = type_is_const(d->ref) ? SECTION_RODATA : SECTION_DATA;
if(d->bits.var.init.dinit && !decl_init_is_zero(d->bits.var.init.dinit)){
asm_nam_begin(sec, d);
asm_declare_init(sec, d->bits.var.init.dinit, d->ref);
asm_out_section(sec, "\n");
}else if(d->bits.var.init.compiler_generated && fopt_mode & FOPT_COMMON){
const char *common_prefix = "comm ";
/* section doesn't matter */
sec = SECTION_BSS;
if(decl_linkage(d) == linkage_internal){
if(AS_SUPPORTS_LOCAL_COMMON){
asm_out_section(sec, ".local %s\n", decl_asm_spel(d));
}else{
common_prefix = "zerofill __DATA,__bss,";
}
}
asm_out_section(sec, ".%s%s,%u,%u\n",
common_prefix,
decl_asm_spel(d), decl_size(d), decl_align(d));
}else{
/* always resB, since we use decl_size() */
asm_nam_begin(SECTION_BSS, d);
asm_reserve_bytes(SECTION_BSS, decl_size(d));
}
}
int decl_unused_and_internal(decl *d)
{
/* need to check every clone of the decl */
decl *i;
int used = 0;
for(i = d; i; i = i->proto){
if(i->flags & DECL_FLAGS_USED){
used = 1;
goto fin;
}
}
for(i = d; i; i = i->impl){
if(i->flags & DECL_FLAGS_USED){
used = 1;
goto fin;
}
}
fin:
return !used && decl_linkage(d) != linkage_external;
}