[英]Tricking Preprocessor VARIADIC MACROS in GCC
I have a task at work to make the static library more secure , in order to do so I need to replace the formatted strings of printf
for them to appear differently in the compiled static library , for this to happen it must be done in the pre processor stage . 我有一个工作要使静态库更安全,为此,我需要替换
printf
的格式化字符串,以使它们在已编译的静态库中以不同的方式出现,为此,必须在预编译中完成处理器阶段。
What I did (and it actually works in visual studio) is the following ( and it is just a pseudo example ): 我所做的(并且它实际上在Visual Studio中有效)是以下内容( 这只是一个伪示例 ):
char * my_array[] = {"abcd", "a %d", " b %d %s "};
#define GENERIC_ARRAY(x) my_array[x]
#define VARIADIC_DEBUG_PRINT(...) DebugPrintFunction (__FILE__, __LINE__, __func__, __VA_ARGS__)
#define PRINT_BY_LEVEL(x) VARIADIC_DEBUG_PRINT x
#define REPLACE_STRING(x,...) PRINT_BY_LEVEL((GENERAL_LEVEL,GENERIC_ARRAY(__COUNTER__),__VA_ARGS__))
#define MY_PRINTF(x,...) REPLACE_STRING((void*)0,(void*)0,__VA_ARGS__)
All of this overhead is for me to trick the compiler to accept prints without any arguments except the string 所有这些开销对我来说都是骗人的,使编译器接受不带任何参数(字符串除外)的打印
So when testing it in my main.c I tried the following And it worked : 因此,当在我的main.c中对其进行测试时,我尝试了以下操作,它确实有效:
MY_PRINTF("Hello World");
MY_PRINTF("My Val %d", i);
MY_PRINTF("MY VAL %d My String %s", i, s);
But when switching to GCC, he does not like the format of the first print ie : 但是当切换到GCC时,他不喜欢第一张纸的格式,即:
MY_PRINTF("Hello World");
And throws me an compilation error : 并抛出一个编译错误:
error: expected expression before ')' token
Any ideas how may I trick the compiler and accept it ? 有什么想法可以欺骗编译器并接受它吗? or maybe better ideas how to rename the string safely after compilation ?
还是更好的主意,如何在编译后安全地重命名字符串?
You can try something like : 您可以尝试类似:
#include <stdio.h>
#define PRINT(x, ...) printf(x, ##__VA_ARGS__)
int main (int argc, char *argv[]) {
PRINT("Hello\n");
PRINT("World %d\n", 42);
return 0;
}
It works with gcc 4.8 (not tried with earlier version, but it should work too) 它适用于gcc 4.8(未尝试使用较早版本,但也应适用)
Using ##__VA_ARGS__
, you may try: 使用
##__VA_ARGS__
,您可以尝试:
#define MY_PRINTF(x, ...) \
VARIADIC_DEBUG_PRINT(GENERAL_LEVEL, GENERIC_ARRAY(__COUNTER__), (void*)0, (void*)0, ##__VA_ARGS__)
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