How can I link my C code with the PCRE library? (Linker errors currently being thrown.)

问题

The Problem

Note: I originally had this problem in a much larger project; so I pared the code down to the test case you see below.

I cannot figure out how to get the following test code to compile. Specifically, it appears as if the linker cannot find the PCRE library (see below for how PCRE was configured). And this despite the explicit -L/usr/local/lib -lpcre being passed to the linker (PCRE is installed in the /usr/local directory structure).

What am I doing wrong? :-(

The console output is:

$ make
rm -f ./*.o
gcc -ansi -Wall -pedantic-errors -I/usr/local/include -g0 -O3 -static -static-libgcc -march=i686 -malign-double -m128bit-long-double -c main.c -o main.o
gcc -ansi -Wall -pedantic-errors -L/usr/local/lib -lpcre -g0 -O3 -static -static-libgcc -march=i686 -malign-double -m128bit-long-double main.o -o pcre_test_1_i686
main.o:main.c:(.text+0x100): undefined reference to `pcre_compile2'
main.o:main.c:(.text+0x12e): undefined reference to `pcre_study'
main.o:main.c:(.text+0x16e): undefined reference to `pcre_exec'
main.o:main.c:(.text+0x19f): undefined reference to `pcre_copy_substring'
collect2: ld returned 1 exit status
make: *** [all] Error 1

Relevant Files

PCRE Configuration and Compile Environment

./configure --disable-shared --enable-static --disable-cpp --enable-rebuild-chartables --enable-utf8 --enable-unicode-properties --enable-newline-is-any --disable-stack-for-recursion --with-posix-malloc-threshold=2 --with-link-size=4

CC="gcc"
CFLAGS="-g0 -O3 -static -static-libgcc -march=i686 -malign-double -m128bit-long-double"
LD_RUN_PATH="/usr/local/include:/usr/local/lib"

main.c

#define PCRE_STATIC  
#include <pcre.h>  
#include <stdlib.h>  
#include <errno.h>  
#include <stdio.h>  
#include <string.h>  

#define OUTPUT_SIZE 12
#define SUBSTRING_SIZE 16

int main(int argc, char *argv[]) {

  pcre *re;
  pcre_extra *extra;
  const char *input = "get food";
  const char *pattern = "^\\s*get\\s+(\\w+)\\s*$\0";
  int options = PCRE_CASELESS | PCRE_UTF8 | PCRE_UCP;
  int error_code = 0;
  int error_offset = 0;
  const char *compile_error;
  const char *study_error;
  int output[OUTPUT_SIZE];
  char substring[SUBSTRING_SIZE];
  int matched = 0;
  int is_error = 0;
  int index = 0;
  for(index = 0; index < OUTPUT_SIZE; index++) {
    output[index] = 0;
  }
  re = pcre_compile2( pattern,
                      options,
                      &error_code,
                      &compile_error,
                      &error_offset,
                      NULL );
  if(re == NULL) {
    fprintf(stderr, "PCRE regular expression error at position %d: %s", error_offset, compile_error);
    exit(EXIT_FAILURE);
  }
  if(error_code == 0) {
    extra = pcre_study( re,
                        0,
                        &study_error );
  }
  else {
    fprintf(stderr, "PCRE regular expression error at position %d: %s", error_offset, compile_error);
    extra = NULL;
  }

  matched = pcre_exec( re,
                       extra,
                       input,
                       (int)strlen(input),
                       0, /* Start at the beginning of the string */
                       0,
                       output,
                       OUTPUT_SIZE );
  if(matched > 1) {
    int status = pcre_copy_substring( input,
                                      output,
                                      matched,
                                      1,
                                      substring,
                                      SUBSTRING_SIZE );
    if(status < 0) {
      switch(status) {
        case PCRE_ERROR_NOMEMORY:
          fprintf(stderr, "PCRE substring extraction error: %s", "Buffer too small");
          break;
        case PCRE_ERROR_NOSUBSTRING:
          fprintf(stderr, "PCRE substring extraction error: %s", "Invalid substring number");
          break;
      }
      is_error = 1;
    }
  }

  printf("Capture group 1 is: '%s'\n", substring);
  if(is_error) {
    printf("There was an error with the pcre_copy_substring() function.\n");
  }

  return EXIT_SUCCESS;
}

Makefile

PACKAGE = pcre_test
VERSION = 1

# -ansi == ANSI C
# -std=iso9899:199409 == ANSI C w/ Amendment 1
# -std=c99 == ISO C99
GCC_CMD = gcc -ansi -Wall -pedantic-errors

# Generic: i686
# Intel: core2, corei7, corei7-avx
# AMD: k8-sse3, opteron-sse3, athlon64-sse3, amdfam10
ARCH = i686

RELEASE_FILE = $(PACKAGE)_$(VERSION)_$(ARCH)

GCC_OPTIONS = -g0 -O3 -static -static-libgcc -march=$(ARCH) -malign-double -m128bit-long-double
GCC_COMPILE = $(GCC_CMD) -I/usr/local/include $(GCC_OPTIONS)
GCC_LINK = $(GCC_CMD) -L/usr/local/lib -lpcre $(GCC_OPTIONS)

GCC_LINK_ALL = $(GCC_LINK) main.o

all: clean build_main
        $(GCC_LINK_ALL) -o $(RELEASE_FILE)

build_main:
        $(GCC_COMPILE) -c main.c -o main.o

clean:
        rm -f ./*.o

[EDIT]

The Answer Has Been Found!

All external library flags must be listed after all of the object files. Thus, the Makefile should have looked like this:

GCC_LINK = $(GCC_CMD) -L/usr/local/lib $(GCC_OPTIONS)

GCC_LINK_ALL = $(GCC_LINK) main.o -lpcre

Thank you to everyone who responded with answers. :-)

回答1:

Is it possible the linker is finding a pre-built version of the libpcre.so?

Try the advice from this question: "specify /usr/local/lib/libpcre.a on the compiler command line ... avoid including -lpcre".

来源：https://stackoverflow.com/questions/6509834/how-can-i-link-my-c-code-with-the-pcre-library-linker-errors-currently-being-t

标签

makefile

linker-errors

pcre