[PATCH v2 0/3] Allow flexible array members in unions and alone in structures [PR53548]

[Qing Zhao <qing.zhao@oracle.com>]

Hi,

This is the 2nd version for 
Allow flexible array members in unions and alone in structures [PR53548]

(for your reference, the 1st version is at:
https://gcc.gnu.org/pipermail/gcc-patches/2024-April/649737.html)

compared to the 1st version, the major difference are:

A. C FE updates based on Joseph's comments:

   documentation changes;

   testing case changes; 
   * added testing cases for -pedantic-errors;
   * renamed the testing cases to accurately reflect the covered tests;
   * added unnamed bit-fields along with FAM;
   * move the testing cases to c-c++-common;

B. Merge the 4th patch (old testing adjustment) to the 2nd patch in order to 
   avoid testing regressions if individual patch is tested separately. 

Approval status:

   C FE and documentation changes have been approved for GCC15 with the above update A. 
   (Patch 1 and Patch 3 have been approved, the C FE part of Patch 2
    has been approved). 

Review needed:

   C++ FE changes (in Patch 2);
   Middle-end changes (in Patch 2);

The patch set includes:
 1. Documentation change.
    Allow flexible array members in unions and alone in structures
    [PR53548]
 2. C and C++ FE changes to support flexible array members in unions and
   alone in structures.
    Adjust testcases for flexible array member in union and alone in
   structure extension.
 3. Add testing cases for flexible array members in unions and alone in
   structures.

bootstrapped and regression tested on both x86 and aarch64, no issue.

Okay for GCC15?

thanks.

Qing