似乎GCC在使用
问题是,为什么最后一个"./test"生成的是"0 1 1",而不是"1 1 1"?
gcc版本5.4.0(GCC)
-O2
和__attribute__((weak))
时,根据您如何引用弱符号而产生不同的结果。请考虑以下代码:
$ cat weak.c#include <stdio.h>
extern const int weaksym1;
const int weaksym1 __attribute__(( weak )) = 0;
extern const int weaksym2;
const int weaksym2 __attribute__(( weak )) = 0;
extern int weaksym3;
int weaksym3 __attribute__(( weak )) = 0;
void testweak(void)
{
if ( weaksym1 == 0 )
{
printf( "0\n" );
}
else
{
printf( "1\n" );
}
printf( "%d\n", weaksym2 );
if ( weaksym3 == 0 )
{
printf( "0\n" );
}
else
{
printf( "1\n" );
}
}
$ cat test.c
extern const int weaksym1;
const int weaksym1 = 1;
extern const int weaksym2;
const int weaksym2 = 1;
extern int weaksym3;
int weaksym3 = 1;
extern void testweak(void);
void main(void)
{
testweak();
}
$ make
gcc -c weak.c
gcc -c test.c
gcc -o test test.o weak.o
$ ./test
1
1
1
$ make ADD_FLAGS="-O2"
gcc -O2 -c weak.c
gcc -O2 -c test.c
gcc -O2 -o test test.o weak.o
$ ./test
0
1
1
问题是,为什么最后一个"./test"生成的是"0 1 1",而不是"1 1 1"?
gcc版本5.4.0(GCC)