user-0 提问: 求助c语言大神。关于php扩展开发中使用第三方库的问题

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user: user-1
content: EXAMPLE Load the math library, and print the cosine of 2.0:  #include <stdio.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(1);     }      dlerror();    /* Clear any existing error */     *(void **) (&cosine) = dlsym(handle, "cos");     if ((error = dlerror()) != NULL)  {         fprintf (stderr, "%s\n", error);         exit(1);     }      printf ("%f\n", (*cosine)(2.0));     dlclose(handle);     return 0; }  If this program were in a file named "foo.c", you would build the program with the following command:   gcc -rdynamic -o foo foo.c -ldl   Libraries exporting _init() and _fini() will want to be compiled as follows, using bar.c as the example name:   gcc -shared -nostartfiles -o bar bar.c

user: user-1
content: LDCONFIG Section: Linux Programmer's Manual (8) Updated: 2002-05-06  --------------------------------------------------------------------------------    NAME /sbin/ldconfig - configure dynamic linker run time bindings    SYNOPSIS /sbin/ldconfig [ -nNvXV ] [ -f conf ] [ -C cache ] [ -r root ] directory ...  /sbin/ldconfig -l [ -v ] library ...   /sbin/ldconfig -p     DESCRIPTION ldconfig creates the necessary links and cache to the most recent shared libraries found in the directories specified on the command line, in the file /etc/ld.so.conf, and in the trusted directories (/lib and /usr/lib). The cache is used by the run-time linker, ld.so or ld-linux.so. ldconfig checks the header and file names of the libraries it encounters when determining which versions should have their links updated.  ldconfig will attempt to deduce the type of ELF libs (ie. libc5 or libc6/glibc) based on what C libs, if any, the library was linked against. Therefore, when making dynamic libraries, it is wise to explicitly link against libc (use -lc).   Some existing libs do not contain enough information to allow the deduction of their type. Therefore, the /etc/ld.so.conf file format allows the specification of an expected type. This is only used for those ELF libs which we can not work out. The format is "dirname=TYPE", where TYPE can be libc4, libc5, or libc6. (This syntax also works on the command line.) Spaces are not allowed. Also see the -p option. ldconfig should normally be run by the superuser as it may require write permission on some root owned directories and files.     OPTIONS -v  Verbose mode. Print current version number, the name of each directory as it is scanned, and any links that are created. Overrides quiet mode.  -n  Only process directories specified on the command line. Don't process the trusted directories (/lib and /usr/lib) nor those specified in /etc/ld.so.conf. Implies -N.  -N  Don't rebuild the cache. Unless -X is also specified, links are still updated.  -X  Don't update links. Unless -N is also specified, the cache is still rebuilt.  -f conf  Use conf instead of /etc/ld.so.conf.  -C cache  Use cache instead of /etc/ld.so.cache.  -r root  Change to and use root as the root directory.  -l  Library mode. Manually link individual libraries. Intended for use by experts only.  -p  Print the lists of directories and candidate libraries stored in the current cache.      FILES /lib/ld.so  run-time linker/loader  /etc/ld.so.conf  File containing a list of colon, space, tab, newline, or comma spearated directories in which to search for libraries.  /etc/ld.so.cache  File containing an ordered list of libraries found in the directories specified in /etc/ld.so.conf.  --------------------------------------------------------------------------------