Re: [Tinycc-devel] Array type not promoted within comma operator

[Herman ten Brugge via Tinycc-devel]

On 12/28/23 15:44, Patrick Pelissier wrote:

Hi,

The following program doesn't compile with tinycc:

typedef int T[2];
int f(T t) {
return _Generic(t, __typeof__( ((void)0,(T){0})) : 1 );
}

whereas I was expecting it to compile (like for GCC/CLANG) due to
"promotion" of "array of int" type to "int pointer" type since it uses
the comma operator.

I made a patch. See attachment.

I cannot find a lot of information on this feature.
Is it a gcc/clang extension?
Does it only apply to typeof?

    Herman

diff --git a/tccgen.c b/tccgen.c
index 29dae91..4d6f91a 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -45,6 +45,7 @@ static Sym *all_cleanups, *pending_gotos;
 static int local_scope;
 static int in_sizeof;
 static int constant_p;
+static int comma_found;
 ST_DATA char debug_modes;
 
 ST_DATA SValue *vtop;
@@ -4782,9 +4783,12 @@ static int parse_btype(CType *type, AttributeDef *ad, 
int ignore_label)
         case TOK_TYPEOF2:
         case TOK_TYPEOF3:
             next();
+           comma_found = 0;
             parse_expr_type(&type1);
             /* remove all storage modifiers except typedef */
             type1.t &= ~(VT_STORAGE&~VT_TYPEDEF);
+           if (comma_found)
+               type1.t &= ~(VT_CONSTANT | VT_VOLATILE | VT_ARRAY);
            if (type1.ref)
                 sym_to_attr(ad, type1.ref);
             goto basic_type2;
@@ -6553,6 +6557,7 @@ ST_FUNC void gexpr(void)
             break;
        constant_p &= (vtop->r & (VT_VALMASK | VT_LVAL)) == VT_CONST &&
                       !((vtop->r & VT_SYM) && vtop->sym->a.addrtaken);
+       comma_found = 1;
         vpop();
         next();
     }
diff --git a/tests/tests2/94_generic.c b/tests/tests2/94_generic.c
index 1cb0164..600b311 100644
--- a/tests/tests2/94_generic.c
+++ b/tests/tests2/94_generic.c
@@ -30,6 +30,12 @@ void void_foo(int i) {}
 
 typedef int int_type1;
 
+typedef int T[2];
+int f(T t)
+{
+       return _Generic(t, __typeof__( ((void)0,(T){0})) : 1 );
+}
+
 #define gen_sw(a) _Generic(a, const char *: 1, default: 8, int: 123);
 
 int main()
@@ -40,6 +46,7 @@ int main()
        const int * const ptr;
        const char *ti;
        int_type1 i2;
+       T t;
 
        i = _Generic(a, int: a_f, const int: b_f)();
        printf("%d\n", i);
@@ -118,5 +125,7 @@ int main()
          (void)(sizeof(struct { int x:_Generic( 0?(int (*)[5])0 : ar, int 
(*)[5]:+1, int (*)[4]:(void)0); }));
        }
 
+       printf ("%d\n", f(t));
+
        return 0;
 }
diff --git a/tests/tests2/94_generic.expect b/tests/tests2/94_generic.expect
index 80d4ed9..79be7ab 100644
--- a/tests/tests2/94_generic.expect
+++ b/tests/tests2/94_generic.expect
@@ -13,3 +13,4 @@ long
 1
 3
 5
+1

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