ID Number: Q67041
6.00 6.00a 6.00ax 7.00 | 6.00 6.00a
MS-DOS | OS/2
buglist6.00 buglist6.00a buglist6.00ax buglist7.00
Summary:
SYMPTOMS
In Microsoft C versions 6.0, 6.0a, 6.0ax, and C/C++ version 7.0,
the following error may be generated:
error C2025: 'tag1': enum/struct/union type redefinition
CAUSE
The scope of an identifier in C is determined by the placement of
its declaration. According to the ANSI specification, if an
identifier's declarator or type specification appears within a list
of parameter declarations in a function prototype, the identifier
is said to have "function prototype scope." This scope terminates
at the end of the function prototype. In the C and QuickC
compilers, this scope is not correctly terminated for structure and
union tags, and a C2025 error may be incorrectly generated.
STATUS
Microsoft has confirmed this to be a problem in C versions 6.0,
6.0a, 6.0ax, and 7.0 and QuickC versions 2.5 and 2.51 (buglist2.50
and buglist2.51). We are researching this problem and will post new
information here as it becomes available.
More Information:
The sample code below demonstrates this problem. The identifier "tag1"
is a struct/union tag that does appear twice, but because the second
instance appears in the prototype for func1(), it should have scope
that is local to the prototype only. The same is true for "num".
Section 3.1.2.1 of the ANSI specification states the following:
If an outer declaration of a lexically identical identifier exists
in the same name space, it is hidden until the current scope
terminates, after which it again becomes visible.
Thus, both of these identifiers should not be visible outside of the
prototype itself. Yet, the compiler correctly allows the name "num" to
be reused, while incorrectly generating the following error for
"tag1":
error C2025: 'tag1' : enum/struct/union type redefinition
Sample Code
-----------
/* Compile options needed: /Za
*/
void main(void)
{
int num;
union tag1 { int i;
float f; };
{
void func1( float num, struct tag1 *ptr );
}
}
Additional reference words: 2.50 6.00 6.00a 6.00ax 2.51 2.5 s_quickc
7.00