c - C语言中printf和printf_s有什么区别？

Question

我只是想知道其中的区别，并且我已经尝试过在 Google 上进行搜索。

printf()printf_s()

Answer 1

今天我学到了一些新东西。我从未使用过 _s 函数，并且始终假设它们是供应商提供的扩展，但它们实际上是在附件 K“边界检查接口(interface)”下的语言标准中定义的。关于printf_s:

K.3.5.3.3 The printf_s function

Synopsis

1 #define _ _STDC_WANT_LIB_EXT1_ _ 1
  #include <stdio.h>
  int printf_s(const char * restrict format, ...);

Runtime-constraints

2 <strong>format</strong> shall not be a null pointer. The %n specifier ³⁹⁴⁾ (modified or not by flags, fieldwidth, or precision) shall not appear in the string pointed to by <strong>format</strong>. Any argumentto <strong>printf_s</strong> corresponding to a <strong>%s</strong> specifier shall not be a null pointer.

3 If there is a runtime-constraint violation, the printf_s function does not attempt toproduce further output, and it is unspecified to what extent <strong>printf_s</strong> produced outputbefore discovering the runtime-constraint violation.

Description

4 The printf_s function is equivalent to the printf function except for the explicitruntime-constraints listed above.

Returns

5 The printf_s function returns the number of characters transmitted, or a negativevalue if an output error, encoding error, or runtime-constraint violation occurred.

---

^{394) It is not a runtime-constraint violation for the characters %n to appear in sequence in the string pointedat by format when those characters are not a interpreted as a %n specifier. For example, if the entireformat string was %%n.}

^{C 2011 Online Draft}

总而言之，printf_s 对 printf 未完成的参数执行额外的运行时验证，并且如果任何运行时验证失败，则不会尝试继续。

_s 函数是可选，编译器不需要支持它们。如果它们受支持，则宏 __STDC_WANT_LIB_EXT1__ 将被定义为 1，因此如果您想使用它们，您需要像

#if __STDC_WANT_LIB_EXT1__ == 1
    printf_s( "%s", "This is a test\n" );
#else
    printf( "%s", "This is a test\n" );
#endif