C语言 如何将 64 位整数打印为十六进制？
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How to printf a 64-bit integer as hex?
提问by sergej
With the following code I am trying to output the value of a unit64_tvariable using printf(). Compiling the code with gcc, returns the following warning:
使用以下代码，我尝试unit64_t使用printf(). 使用 gcc 编译代码，返回以下警告：
warning: format ‘%x' expects argument of type ‘unsigned int', but argument 2 has type ‘uint64_t' [-Wformat=]
警告：格式 '%x' 需要类型为 'unsigned int' 的参数，但参数 2 的类型为 'uint64_t' [-Wformat=]
The code:
编码：
#include <stdio.h>
#include <stdint.h>
int main ()
{
uint64_t val = 0x1234567890abcdef;
printf("val = 0x%x\n", val);
return 0;
}
The output:
输出：
val = 0x90abcdef
Expected output:
预期输出：
val = 0x1234567890abcdef
How can I output a 64bit value as a hexadecimal integer using printf()? The xspecifier seems to be wrong in this case.
如何使用 将 64 位值输出为十六进制整数printf()？x在这种情况下，说明符似乎是错误的。
回答by tangrs
The warning from your compiler is telling you that your format specifier doesn't match the data type you're passing to it.
编译器的警告告诉您格式说明符与传递给它的数据类型不匹配。
Try using %lxor %llx. For more portability, include inttypes.hand use the PRIx64macro.
尝试使用%lx或%llx。为了获得更多的可移植性，请包含inttypes.h并使用PRIx64宏。
For example: printf("val = 0x%" PRIx64 "\n", val);(note that it's string concatenation)
例如：（printf("val = 0x%" PRIx64 "\n", val);注意它是字符串连接）
回答by Superlokkus
Edit: Use printf("val = 0x%" PRIx64 "\n", val);instead.
编辑：改为使用printf("val = 0x%" PRIx64 "\n", val);。
Try printf("val = 0x%llx\n", val);. See the printf manpage:
试试printf("val = 0x%llx\n", val);。请参阅printf 联机帮助页：
ll (ell-ell). A following integer conversion corresponds to a long long int or unsigned long long int argument, or a following n conversion corresponds to a pointer to a long long int argument.
我（嗯）。后面的整数转换对应于 long long int 或 unsigned long long int 参数，或者后面的 n 转换对应于指向 long long int 参数的指针。
Edit: Even better is what @M_Oehm wrote: There is a specific macro for that, because unit64_tis not always a unsigned long long: PRIx64see also this stackoverflow answer
编辑：更好的是@M_Oehm 写道：有一个特定的宏，因为unit64_t并不总是一个unsigned long long：PRIx64另见这个stackoverflow answer
