ppci-cc: impossible to redefine a struct/union/enum tag in inner scopes

[tstreiff]

C Struct/union/enum tags follow the same rules than other identifiers for scope. They may be redeclared in an inner scope and the inner declaration hides the outer ones.
The following legal code is reported as erroneous :

void f(int n) {
struct S { int a; };
if (n == 10) {
struct S { int b; } s; // error "multiple definitions"
s.b = 1;
}
s.a = 2;
}
4: struct S { int b; } s;
^ Multiple definitions
2020-01-22 00:37:59,248 | INFO | root | ppci 0.5.7 on CPython 3.6.9 on Linux
2020-01-22 00:37:59,254 | INFO | cbuilder | Starting C compilation (c99)
2020-01-22 00:37:59,256 | ERROR | root | Multiple definitions
2020-01-22 00:37:59,257 | ERROR | root | (bug20.c, 5, 5)

Same behaviour for union/enum (which share the tag namespace)

[windelbouwman]

Agreed, verified this was implemented wrongly. Addressed in 2ac2d76.