无法在 C 中使用我的库

Question

我使用的是 OS X 机器，并且我用 C 语言编写了一个库，我将在以后的程序中使用它。

这是声明：(FunzioniListe.h)

#ifndef FUNZIONILISTE_H
#define FUNZIONILISTE_H

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

struct node {
    int nodeValue;
    char elem;
    struct node *next;
};

struct node *addElemToList(struct node *list, int position, int value, char elemToAdd);

void deleteElem(struct node *list, int value);    
int listLen(struct node *list);    
void printList(struct node *list);

#endif // FUNZIONILISTE_H_INCLUDE

这是实现：(FunzioniListe.c)

#include <stdio.h>
#include <stdlib.h>
#include "FunzioniListe.h"

struct node *addElemToList(struct node *list, int position, int value, char elemToAdd) {
    struct node *newNode;
    newNode = malloc(sizeof(struct node));

    if (newNode == NULL) {
        printf("Error: malloc failed");
        exit(EXIT_FAILURE);
    }

    newNode->elem = elemToAdd;
    newNode->nodeValue = value;

    if (position > listLen(list)) {
        while (list->next != NULL) {
            list = list->next;
        }
        list->next = newNode;
    } else {
        int counter = 0;
        while (counter < position) {
            list = list->next;
        }
        newNode->next = list->next;
        list->next = newNode;
    }
    return newNode;
}

void deleteElem(struct node *list, int position) {
    int counter = 0;
    struct node *elemToDelete;
    if (position > 0 && position < listLen(list)) {
        while (counter < (position - 1)) {
            list = list->next;
        }
        elemToDelete = list->next;
        list->next = elemToDelete->next;
        free(elemToDelete);
    } else {
        while (counter < (listLen(list) - 1)) {
            list = list->next;
        }
        elemToDelete = list->next;
        free(elemToDelete);
    }
}

int listLen(struct node *list) {
    int listLen = 0;
    for (; list != NULL; list = list->next) {
        listLen++;
    }
    return listLen;
}

void printList(struct node *list) {
    for (; list != NULL; list = list->next) {
        printf("Node #%d\nElem: %c\n\n", list->nodeValue, list->elem);
    }
}

问题是当我尝试在另一个项目中使用这个库时，我得到了这个输出：

Undefined symbols for architecture x86_64:
  "_addElemToList", referenced from:
      _main in TestLibreria-ef7c77.o
  "_printList", referenced from:
      _main in TestLibreria-ef7c77.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

这是一个利用已创建库的简单程序：

#include <stdlib.h>
#include <stdio.h>
#include "FunzioniListe.h"

int main() {
    struct node *first = NULL;
    for (int i = 0; i < 7; i++) {
        first = addElemToList(first, 30, i, i + 60);
    }
    printList(first);
}

我不明白问题出在哪里，两个文件都是正确的，但我的 Mac 无法正确编译。 为什么会发生这种情况？

深度调用错误：

Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.2.0
Thread model: posix
 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.11.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -main-file-name TestLibreria.c -mrelocation-model pic -pic-level 2 -mthread-model posix -mdisable-fp-elim -masm-verbose -munwind-tables -target-cpu core2 -target-linker-version 253.9 -v -dwarf-column-info -resource-dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/7.0.2 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -fdebug-compilation-dir /Users/Matt/CProjects/Lab -ferror-limit 19 -fmessage-length 195 -stack-protector 1 -mstackrealign -fblocks -fobjc-runtime=macosx-10.11.0 -fencode-extended-block-signature -fmax-type-align=16 -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/1c/6dpsqcrs69s9hgdnj0kkyh780000gn/T/TestLibreria-a8db8d.o -x c TestLibreria.c
clang -cc1 version 7.0.2 based upon LLVM 3.7.0svn default target x86_64-apple-darwin15.2.0
ignoring nonexistent directory "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/local/include"
ignoring nonexistent directory "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/7.0.2/include
 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include
 /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks (framework directory)
End of search list.
 "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld" -demangle -dynamic -arch x86_64 -macosx_version_min 10.11.0 -syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -o a.out /var/folders/1c/6dpsqcrs69s9hgdnj0kkyh780000gn/T/TestLibreria-a8db8d.o -lSystem /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/7.0.2/lib/darwin/libclang_rt.osx.a
Undefined symbols for architecture x86_64:
  "_addElemToList", referenced from:
      _main in TestLibreria-a8db8d.o
  "_printList", referenced from:
      _main in TestLibreria-a8db8d.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Answer 1

你没有链接它们。

您可能只使用gcc -std=c99 main.c（假设这是最后一个的名称）。然后使用的功能不会被引用。在 Linux Mint 17.1 Rebecca 上运行它之后，我得到了

/tmp/ccOdy4br.o：在函数main': main.c:(.text+0x32): undefined reference toaddElemToList' main.c:(.text+0x4c): undefined reference to `printList' collect2：错误：ld 返回 1 个退出状态

所以你应该尝试使用链接标志

gcc -std=c99 -c *.c

然后编译

gcc -std=c99 *.o

然后我能够运行它并成功地得到一个分段错误。

注意：* 是 any 的正则表达式，它在终端中工作，因为 Mac 是基于 Unix 的。

Answer 2

创建 C 库的步骤

---

1. 创建库接口

   ---

   • 为您的库函数的用户提供带有 cmets 的函数原型
   • 您的库导出的类型和全局变量的定义

2. 创建库的实现

   ---

   • 库中每个函数的实现

3. 创建库对象文件

   ---

当您拥有 library.h 接口及其 library.c 实现后，您所要做的就是运行此命令

gcc -o library.o -c library.c

4. 在另一个 C 程序中使用该库

   ---

   • 在您的代码中使用#include "libraryname.h"

我的代码中缺少的是第 3 步。

现在我可以通过命令编译使用我的库的 C 程序

gcc cprogram.c library.o