c - compilint PCRE c 代码中体系结构 x86_64 的 undefined symbol

Question

我有一个使用 PCRE 库的简单代码。我只是想知道有关 pcre 的 c 代码，因此从 http://www.mitchr.me/SS/exampleCode/AUPG/pcre_example.c.html 复制了代码

#include <pcre.h>               /* PCRE lib        NONE  */
#include <stdio.h>              /* I/O lib         C89   */
#include <stdlib.h>             /* Standard Lib    C89   */
#include <string.h>             /* Strings         C89   */

/**********************************************************************************************************************************/
int main(int argc, char *argv[]) {
  pcre *reCompiled;
  pcre_extra *pcreExtra;
  int pcreExecRet;
  int subStrVec[30];
  const char *pcreErrorStr;
  int pcreErrorOffset;
  char *aStrRegex;
  char **aLineToMatch;
  const char *psubStrMatchStr;
  int j;
  char *testStrings[] = { "This should match... hello",
                          "This could match... hello!",
                          "More than one hello.. hello",
                          "No chance of a match...",
                          NULL};


  aStrRegex = "(.*)(hello)+";  
  printf("Regex to use: %s\n", aStrRegex);

  // First, the regex string must be compiled.
  reCompiled = pcre_compile(aStrRegex, 0, &pcreErrorStr, &pcreErrorOffset, NULL);

  /* OPTIONS (second argument) (||'ed together) can be:
       PCRE_ANCHORED       -- Like adding ^ at start of pattern.
       PCRE_CASELESS       -- Like m//i
       PCRE_DOLLAR_ENDONLY -- Make $ match end of string regardless of \n's
                              No Perl equivalent.
       PCRE_DOTALL         -- Makes . match newlins too.  Like m//s
       PCRE_EXTENDED       -- Like m//x
       PCRE_EXTRA          -- 
       PCRE_MULTILINE      -- Like m//m
       PCRE_UNGREEDY       -- Set quantifiers to be ungreedy.  Individual quantifiers
                              may be set to be greedy if they are followed by "?".
       PCRE_UTF8           -- Work with UTF8 strings.
  */

  // pcre_compile returns NULL on error, and sets pcreErrorOffset & pcreErrorStr
  if(reCompiled == NULL) {
    printf("ERROR: Could not compile '%s': %s\n", aStrRegex, pcreErrorStr);
    exit(1);
  } /* end if */

  // Optimize the regex
  pcreExtra = pcre_study(reCompiled, 0, &pcreErrorStr);

  /* pcre_study() returns NULL for both errors and when it can not optimize the regex.  The last argument is how one checks for
     errors (it is NULL if everything works, and points to an error string otherwise. */
  if(pcreErrorStr != NULL) {
    printf("ERROR: Could not study '%s': %s\n", aStrRegex, pcreErrorStr);
    exit(1);
  } /* end if */

  for(aLineToMatch=testStrings; *aLineToMatch != NULL; aLineToMatch++) {
    printf("String: %s\n", *aLineToMatch);
    printf("        %s\n", "0123456789012345678901234567890123456789");
    printf("        %s\n", "0         1         2         3");

    /* Try to find the regex in aLineToMatch, and report results. */
    pcreExecRet = pcre_exec(reCompiled,
                            pcreExtra,
                            *aLineToMatch, 
                            strlen(*aLineToMatch),  // length of string
                            0,                      // Start looking at this point
                            0,                      // OPTIONS
                            subStrVec,
                            30);                    // Length of subStrVec

    /* pcre_exec OPTIONS (||'ed together) can be:
       PCRE_ANCHORED -- can be turned on at this time.
       PCRE_NOTBOL
       PCRE_NOTEOL
       PCRE_NOTEMPTY */

    // Report what happened in the pcre_exec call..
    //printf("pcre_exec return: %d\n", pcreExecRet);
    if(pcreExecRet < 0) { // Something bad happened..
      switch(pcreExecRet) {
      case PCRE_ERROR_NOMATCH      : printf("String did not match the pattern\n");        break;
      case PCRE_ERROR_NULL         : printf("Something was null\n");                      break;
      case PCRE_ERROR_BADOPTION    : printf("A bad option was passed\n");                 break;
      case PCRE_ERROR_BADMAGIC     : printf("Magic number bad (compiled re corrupt?)\n"); break;
      case PCRE_ERROR_UNKNOWN_NODE : printf("Something kooky in the compiled re\n");      break;
      case PCRE_ERROR_NOMEMORY     : printf("Ran out of memory\n");                       break;
      default                      : printf("Unknown error\n");                           break;
      } /* end switch */
    } else {
      printf("Result: We have a match!\n");

      // At this point, rc contains the number of substring matches found...
      if(pcreExecRet == 0) {
        printf("But too many substrings were found to fit in subStrVec!\n");
        // Set rc to the max number of substring matches possible.
        pcreExecRet = 30 / 3;
      } /* end if */

      // Do it yourself way to get the first substring match (whole pattern):
      // char subStrMatchStr[1024];
      // int i, j
      // for(j=0,i=subStrVec[0];i<subStrVec[1];i++,j++) 
      //   subStrMatchStr[j] = (*aLineToMatch)[i];
      // subStrMatchStr[subStrVec[1]-subStrVec[0]] = 0;
      //printf("MATCHED SUBSTRING: '%s'\n", subStrMatchStr);

      // PCRE contains a handy function to do the above for you:
      for(j=0; j<pcreExecRet; j++) {
        pcre_get_substring(*aLineToMatch, subStrVec, pcreExecRet, j, &(psubStrMatchStr));
        printf("Match(%2d/%2d): (%2d,%2d): '%s'\n", j, pcreExecRet-1, subStrVec[j*2], subStrVec[j*2+1], psubStrMatchStr);
      } /* end for */

      // Free up the substring
      pcre_free_substring(psubStrMatchStr);
    }  /* end if/else */
    printf("\n");

  } /* end for */

  // Free up the regular expression.
  pcre_free(reCompiled);

  // Free up the EXTRA PCRE value (may be NULL at this point)
  if(pcreExtra != NULL)
    pcre_free(pcreExtra);




  // We are all done..
  return 0;

} /* end func main */

运行程序时

gcc -o test  -I/usr/local/Cellar/pcre/8.35/include -L/usr/local/Cellar/pcre/8.35/lib  simple_pcre.c 

给出错误为

Undefined symbols for architecture x86_64:
  "_pcre_compile", referenced from:
      _main in ccn0k76z.o
  "_pcre_exec", referenced from:
      _main in ccn0k76z.o
  "_pcre_free", referenced from:
      _main in ccn0k76z.o
  "_pcre_free_substring", referenced from:
      _main in ccn0k76z.o
  "_pcre_get_substring", referenced from:
      _main in ccn0k76z.o
  "_pcre_study", referenced from:
      _main in ccn0k76z.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

我应该如何使用 Pcre 库编译 C 代码？

Answer 1

您正在使用 -L 标志进行编译，该标志告诉链接器在哪里可以找到库，但我没有看到带有要链接的实际库的 -l 标志。