From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux 2.4.2-2smp i686; en-US; 0.8.1) Gecko/20010430 Description of problem: gcc-2.96-81 refuses to initialize one const int with an expression containing the value of another constant integer, exiting with the error "initializer element is not constant". How reproducible: Always Steps to Reproduce: 1.Save attached file as "testconst.c" 2."gcc -o testconst testconst.c" 3. Actual Results: testconst.c:3: initializer element is not constant Expected Results: Successful compilation Additional info: egcs-1.1.2 exits with the same error. According to the (year old) gcc-bugs post archived at the above URL, gcc-2.95.2 compiles this code as expected. I'm not 100% certain that initializing one const from another is valid ANSI C (my copy of K doesn't bring up the problem), but I can't see why it wouldn't be allowed.
Created attachment 20050 [details] minimal demonstration source code
From my testing gcc-2.95.2 does not accept it either. Some legalesse: 6.6.6 An integer constant expression shall have integer type and shall only have operands that are integer constants, enumeration constants, character constants, sizeof expressions whose results are integer constants, and floating constants that are the immediate operands of casts. Cast operators in an integer constant expression shall only convert arithmetic types to integer types, except as part of an operand to the sizeof operator. 6.6.7 More latitude is permitted for constant expressions in initializers. Such a constant expression shall be, or evaluate to, one of the following: - an arithmetic constant expression, - a null pointer constant, - an address constant, or - an address constant for an object type plus or minus an integer constant expression. 6.6.10 An implementation may accept other forms of constant expressions. 6.7.8.4 All the expressions in an initializer for an object that has static storage duration shall be constant expressions or string literals. (only included the relevant paragraphs). As you can see, your program is not valid ISO C, but according to 6.6.10 gcc could decide to accept it as constant expression, but it does not have to (unlike in C++). None of egcs 1.1.x, gcc 2.95.x, gcc-2.96-RH, gcc 3.0 or gcc 3.1 accept this.