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Language Extensions
This is most useful if the test modifies the value in some way, for example:
i++ : j;
where i++ comes from a macro. If you write code in this way, then i++ is evaluated only
once.
If the original value of i is nonzero, the result is the original value of i. Regardless of
this, i is incremented once.
Mode
Supported in GNU mode only. Supported languages are C90, C99 and C++.
3.7.8 Designated inits
As in C99, designated initializers are supported.
Example
int a[6] = { [4] = 29, [2] = 15 };
int b[6] = { 0,0,15,0,29,0 }; // a[] is equivalent to b[]
Mode
Supported in GNU mode for C90 and C++ only.
See also
• New features of C99 on page 5-45 in the Compiler User Guide.
3.7.9 Extended lvalues
The definition of what constitutes an lvalue when looking at comma expressions and :
constructs is relaxed in GNU mode. You can use compound expressions, conditional
expressions, and casts as follows:
• You can assign a compound expression:
(a++, b) += x;
This is equivalent to:
temp = (a++,b);
b = temp + x
• You can get the address of a compound expression &(a, b). This is equivalent to
(a, &b).
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