dlerror

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本文介绍如何利用dlerror()函数在C语言中检测动态链接库操作如dlopen(), dlsym()和dlclose()时发生的错误，并通过实例展示了错误处理流程。

http://linux.die.net/man/3/dlerror

dllerror(): 当动态链接库操作函数执行失败时，dlerror可以返回出错信息，返回值为NULL时表示操作函数执行成功。

The function dlerror() returns a human readable string describing the most recent error that occurred from dlopen(), dlsym() or dlclose() since the last call to dlerror(). It returns NULL if no errors have occurred since initialization or since it was last called.


#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>


int main(int argc, char **argv)
{
    void *handle;
    double (*cosine)(double);
    char *error;


    handle = dlopen("libm.so", RTLD_LAZY);
    if (!handle) {
        fprintf(stderr, "%s\n", dlerror());
        exit(EXIT_FAILURE);
    }


    dlerror();    /* Clear any existing error */


    /* Writing: cosine = (double (*)(double)) dlsym(handle, "cos");
       would seem more natural, but the C99 standard leaves
       casting from "void *" to a function pointer undefined.
       The assignment used below is the POSIX.1-2003 (Technical
       Corrigendum 1) workaround; see the Rationale for the
       POSIX specification of dlsym(). */


    *(void **) (&cosine) = dlsym(handle, "cos");


    if ((error = dlerror()) != NULL)  
    {
        fprintf(stderr, "%s\n", error);
        exit(EXIT_FAILURE);
    }


    printf("%f\n", (*cosine)(2.0));
    dlclose(handle);
    exit(EXIT_SUCCESS);
}