android - 'signed size_t' 与 'ssize_t' 不同吗？

Question

当我使用 ndk-build 编译时，它显示一条错误消息:

warning: format '%zd' expects argument of type 'signed size_t', but argument 5 has type 'ssize_t'.

我认为 ssize_t 与 signed size_t 相同，我错了吗？

Answer 1

在Android中，size_t是unsigned int，而ssize_t是long int。要打印或记录 ssize_t，只需使用 "%ld"。

参见 sys/types.h :

Traditionally, bionic's ssize_t was long int. This caused GCC to emit warnings when you pass a ssize_t to a printf()-style function. The correct type is __kernel_ssize_t, which is int, which isn't an ABI change for C code (because they're the same size) but is an ABI change for C++ because int and long int mangle to i and l respectively. So until we can fix the ABI, this change should not be propagated to the NDK.

请注意，在其他平台上，使用%zd 是preferable .