Linux 关于 printf() long unsigned int 和 uint32_t 的编译器警告
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Compiler warning about printf() long unsigned int and uint32_t
提问by pr1268
In my C code, I'm fprintfing a "%lu"and giving a uint32_tfor the corresponding field. But, when I compile with -Wallin GCC (ver. 4.2.4), I get the following warning:
在我的 C 代码中，我fprintf输入了 a"%lu"并uint32_t为相应的字段给出了 a 。但是，当我-Wall在 GCC (ver. 4.2.4) 中编译时，我收到以下警告：
writeresults.c:16: warning: format '%4lu' expects type 'long unsigned int', but argument 2 has type
`uint32_t'
Aren't a uint32_tand long unsigned intthe same thing on 32-bit architectures? Can this warning be avoided without eliminating the -Wallcompiler switch or using a typecast (and if so, how)?
是不是uint32_t和long unsigned int32位架构是一回事吗？在不消除-Wall编译器开关或使用类型转换的情况下是否可以避免此警告（如果是，如何）？
Yes, I'm still using a 32-bit computer/arch/OS/compiler (too poor at the moment to afford new 64-bit HW). Thanks!
是的，我仍在使用 32 位计算机/架构/操作系统/编译器（目前太穷，无法负担新的 64 位硬件）。谢谢！
采纳答案by Conrad Meyer
uint32_ton x86 Linux with GCC is just unsigned int. So use fprintf(stream, "%4u", ...)(unsigned int) or better yet, fprintf(stream, "%4" PRIu32, ...)(the inttypes.hprintf-string specifier for uint32_t).
uint32_t在带有 GCC 的 x86 Linux 上只是unsigned int. 因此，请使用fprintf(stream, "%4u", ...)(unsigned int) 或更好的方法，fprintf(stream, "%4" PRIu32, ...)（用于 的inttypes.hprintf 字符串说明符uint32_t）。
The latter will definitely eliminate the compiler warning / error, and, additionally, is cross-platform.
后者肯定会消除编译器警告/错误，此外，它是跨平台的。
回答by gparent
"long int" and "int" are different types in C++. You might be looking for the "u" format, which stands for "unsigned int". Of course, this depends on what "uint32_t" is a typedef for on your compiler.
“long int”和“int”在 C++ 中是不同的类型。您可能正在寻找“u”格式，它代表“unsigned int”。当然，这取决于编译器上的“uint32_t”是什么类型的定义。
回答by William Pursell
The easiest way to reliably suppress the warning is with a cast:
可靠地抑制警告的最简单方法是使用强制转换：
printf( "%lu", ( unsigned long )x );
