未记录的 GCC 扩展:结构中的 VLA

2021-12-21 00:00:00 gcc memory g++ c++ variable-length-array

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.

相关文章