未记录的 GCC 扩展:结构中的 VLA
在阅读 Clang 文档时，我发现了以下有趣的花絮:[1]
While reading the Clang documentation, I came across the following intriguing tidbit: [1]
clang 不支持允许在结构中使用可变长度数组的 gcc 扩展.这有几个原因:一，实现起来很棘手，二，扩展完全没有记录，三，扩展似乎很少使用.请注意，clang 确实支持灵活的数组成员(结构末尾具有零或未指定大小的数组).
clang does not support the gcc extension that allows variable-length arrays in structures. This is for a few reasons: one, it is tricky to implement, two, the extension is completely undocumented, and three, the extension appears to be rarely used. Note that clang does support flexible array members (arrays with a zero or unspecified size at the end of a structure).
这个扩展怎么用?我的理解是，在构造函数中使用 alloca 会导致堆栈指针在调用函数的末尾恢复，在这种情况下，它将是构造函数――而不是在封闭结构的末尾.
How can this extension be used? My understanding is that using alloca within a constructor causes the stack pointer to be restored at the end of the calling function, which in this case would be the constructor -- not at the end of the enclosing struct.
感谢您的帮助！
推荐答案
参见 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37428
还有 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42121
是的，这很奇怪.
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