GCC comes with Mac OS X 10.4.x and 10.5.x doesn’t support flexible array member

According to GCC manual, it supports flexible array member.

struct foo { int x; int y[]; };
    struct bar { struct foo z; };

    struct foo a = { 1, { 2, 3, 4 } };        // Valid.
    struct bar b = { { 1, { 2, 3, 4 } } };    // Invalid.
    struct bar c = { { 1, { } } };            // Valid.

The lines commented as valid should be compiled without any error. However, the GCC 4.x installed with the Xcode 2.5 and 3.x on OS X 10.4.x and 10.5.x respectively doesn’t compile it without errors.

I reported this bug to the Apple.

NEW on April, 22, 2008
I got message from Apple.

This is a follow-up to Bug ID# 5857390. Engineering has determined that this issue behaves as intended based on the following information:

Page 232 of the GCC manual available at http://gcc.gnu.org/onlinedocs/gcc-4.2.3/gcc.pdf states that:

“To avoid undue complication and confusion with initialization of deeply nested arrays, we simply disallow any non-empty initialization except when the structure is the top-level ob ject.”

Compiling the example on page 232 will produce an error based on the two disallowed statements specifically marked as “Invalid”. Compiling the file with only the “Valid” lines works correctly.


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