https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121209
Bug ID: 121209
Summary: Taking the composite type twice of two structure,
union, or enumerated types yields different results
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: luigighiron at gmail dot com
Target Milestone: ---
The following two programs demonstrate how GCC will compute the composite type
of two types differently when done multiple times:
struct A{int h;};
int main(){
extern struct A x,y;
struct A{int h;};
extern struct A x,y;
typedef typeof(x)T;
typedef typeof(y)T;
}
typedef enum E{h}A;
int main(){
typedef enum E{h}B;
extern A x;
extern B x;
extern B y;
extern A y;
typedef typeof(x)T;
typedef typeof(y)T;
}
In the first program, x and y are both declared with a structure type then
redeclared with another structure type. The declaration of x and y use the same
structure type, and the redeclaration of x and y use the same structure type.
Intuitively, x and y should have the same type but GCC does not give them the
same type as evidenced by the second declaration of T generating an error.
The second program does something similar but instead of structure types it
uses enumerated types, and the order of declarations with y is reversed.
Intuitively, the order of these declarations shouldn't matter but GCC does not
agree as evidenced by the second declaration of T generating an error. Swapping
the order of the declarations of y will make the program work, unlike with
structure or union types.
