Hello,
I'm attempting to get this WG14 proposal
<http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2901.htm#wording-6.2.1p1>
(N2901)
working in TinyCC, based off of this diff from JeanHeyd Meneide
<https://github.com/llvm/llvm-project/compare/main...ThePhD:dang-features/transparent-aliases>.
To summarize, "typedef, but for functions".
Assuming the following definition:
int __callme(int x) { return x; }
I would like this:
_Alias callme = __callme;
to be equivalent to the following declaration:
extern int callme(int x) __asm__("__callme"); // or
__attribute__((alias("__callme")));
In this patch, I can access the alias target and the alias identifier, I
think I just need to push the symbol with the alias identifier, with the
alias_target property set to the alias target's token. Suggestions, advice,
or "here be dragons" are all appreciated.
Cheers,
Asher Mancinelli
---
tccgen.c | 41 ++++++++++++++++++++++++++++++++++++++++-
tcctok.h | 1 +
2 files changed, 41 insertions(+), 1 deletion(-)
diff --git a/tccgen.c b/tccgen.c
index 67e205b..f391a4e 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -5028,6 +5028,38 @@ static void sym_to_attr(AttributeDef *ad, Sym *s)
merge_funcattr(&ad->f, &s->f);
}
+/* Create a symbol with the name of the alias source, set asm label to the
+ * alias target. Return the alias's symbol. */
+static Sym* parse_transparent_alias_decl(AttributeDef *ad, CType *t)
+{
+ int target;
+ int alias = tok;
+ Sym *target_sym;
+
+ if (alias < TOK_UIDENT)
+ expect("identifier");
+
+ printf("Got alias '%s'", get_tok_str(alias, NULL));
+
+ next();
+ skip('=');
+
+ target = tok;
+
+ printf("Got alias target '%s'", get_tok_str(target, NULL));
+
+ target_sym = sym_find(target);
+ *t = target_sym->type;
+ const char* target_str = get_tok_str(target, NULL);
+
+ if (!target_sym) {
+ tcc_error("alias target '%s' is undefined", target_str);
+ }
+
+ ad->alias_target = target;
+ return sym_find(alias);
+}
+
/* Add type qualifiers to a type. If the type is an array then the
qualifiers
are added to the element type, copied because it could be a typedef. */
static void parse_btype_qualify(CType *type, int qualifiers)
@@ -5172,6 +5204,14 @@ static int parse_btype(CType *type, AttributeDef *ad)
goto basic_type2;
}
break;
+
+ case TOK__Alias:
+ next();
+ tcc_warning("_Alias is a non-standard extension");
+ s = parse_transparent_alias_decl(ad, type);
+ // sym_to_attr(ad, s);
+ return 1;
+
case TOK_CONST1:
case TOK_CONST2:
case TOK_CONST3:
@@ -6261,7 +6301,6 @@ ST_FUNC void unary(void)
vpushsym(&s->type, s);
next();
break;
-
case TOK_GENERIC:
{
CType controlling_type;
diff --git a/tcctok.h b/tcctok.h
index d4c1ef5..615b277 100644
--- a/tcctok.h
+++ b/tcctok.h
@@ -19,6 +19,7 @@
DEF(TOK_CASE, "case")
DEF(TOK__Atomic, "_Atomic")
+ DEF(TOK__Alias, "_Alias") /* Strong transparent symbol alias */
DEF(TOK_CONST1, "const")
DEF(TOK_CONST2, "__const") /* gcc keyword */
DEF(TOK_CONST3, "__const__") /* gcc keyword */
--
2.28.0
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