Question

当我使用project运行valgrind时，我收到错误报告。如果我不使用Valgrind，那么该程序看似正常，但我确定Valgrind报告它时出现了问题。

==21286== Invalid read of size 4
==21286==    at 0x404950: fork_pipeline (util.c:296)
==21286==    by 0x403149: execute_pipeline (main.c:177)
==21286==    by 0x4032D5: run_cmd (main.c:221)
==21286==    by 0x403CC3: command (main.c:622)
==21286==    by 0x402B01: main (main.c:933)
==21286==  Address 0x593be68 is 0 bytes after a block of size 24 alloc'd
==21286==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==21286==    by 0x4031DD: run_cmd (main.c:204)
==21286==    by 0x403CC3: command (main.c:622)
==21286==    by 0x402B01: main (main.c:933)

违规main.c:204是

行

`struct pipeline *pipe = malloc(chunks->pipes * sizeof *pipe);`

但我不明白它有什么问题。如果我检查pipes的值，那么它似乎是正确的。周围的代码是：

int run_cmd(const char *cmd) {

    char buffer[2];
    buffer[0] = '|';
    buffer[1] = '\0';
    struct str_list *chunks = list_split(cmd, buffer);
    struct pipeline *pipe = malloc(chunks->pipes * sizeof *pipe);
    pipe->data = malloc(sizeof(char *));
    int i = 0;
    for (i = 0; i < chunks->pipes; i++) {
        pipe[i].data = malloc(sizeof(char *) * BUFFER_SIZE * chunks[i].size);
        int j = 0;
        pipe[i].size = chunks[i].size;
        for (j = 0; j < chunks[i].size; j++) {
            if (chunks[i].argv[j] == NULL) {
                chunks[i].argv[j] = '\0';
                break;
            }
            pipe[i].data[j] = strdup(chunks[i].argv[j]);
            pipe[i].option[0] = chunks[i].option[i];
        }
        pipe[i].data[j] = '\0';
    }
    int status = execute_pipeline(chunks->pipes, pipe);
    return status;
}

如果我查看调试器，那么值看起来不错。我现在的想法是插入断言，以便找到错误出现的位置。

结构有这个声明。

struct str_list {
    char *name;
    int size;
    int pipes;
    char **argv;
    int option[];

};

第二个结构是

struct pipeline {
    char *name;
    int size;
    char **data;
    int option[];
};

更新/编辑

我根据答案更改了代码。

int run_cmd(const char *cmd) {

    char buffer[2];
    buffer[0] = '|';
    buffer[1] = '\0';
    struct str_list *chunks = list_split(cmd, buffer);
    struct pipeline *pipe = malloc(chunks->pipes * sizeof *pipe);
    int i = 0;
    for (i = 0; i < chunks->pipes; i++) {
        pipe[i].data = malloc(sizeof(char **) * BUFFER_SIZE * chunks[i].size);
        int j = 0;
        pipe[i].size = chunks[i].size;
        for (j = 0; j < chunks[i].size; j++) {
            if (chunks[i].argv[j] == NULL) {
                chunks[i].argv[j] = '\0';
                break;
            }
            pipe[i].data[j] = strdup(chunks[i].argv[j]);
            pipe[i].option[0] = chunks[i].option[i];
        }
        pipe[i].data[j] = '\0';
    }
    int status = execute_pipeline(chunks->pipes, pipe);
    return status;
}

仍然无效阅读。

==23103== Invalid write of size 4
==23103==    at 0x403278: run_cmd (main.c:216)
==23103==    by 0x403CB3: command (main.c:621)
==23103==    by 0x402B01: main (main.c:932)
==23103==  Address 0x592e228 is 0 bytes after a block of size 24 alloc'd
==23103==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==23103==    by 0x4031DD: run_cmd (main.c:204)
==23103==    by 0x403CB3: command (main.c:621)
==23103==    by 0x402B01: main (main.c:932)
==23103== 
==23104== Invalid read of size 4
==23104==    at 0x404940: fork_pipeline (util.c:296)
==23104==    by 0x403149: execute_pipeline (main.c:177)
==23104==    by 0x4032C5: run_cmd (main.c:220)
==23104==    by 0x403CB3: command (main.c:621)
==23104==    by 0x402B01: main (main.c:932)
==23104==  Address 0x592e228 is 0 bytes after a block of size 24 alloc'd
==23104==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==23104==    by 0x4031DD: run_cmd (main.c:204)
==23104==    by 0x403CB3: command (main.c:621)
==23104==    by 0x402B01: main (main.c:932)

第216行：pipe[i].option[0] = chunks[i].option[i];

第204行：struct pipeline *pipe = malloc(chunks->pipes * sizeof *pipe);

Answer 1

查看 valgrind 输出，

似乎内存分配为pipe->data 最初，数量由char *类型反映（x86平台上的，通常是1个字节，在其他字节上它可能因编译器和平台定义的实现而变化，然后在for循环中，用实际字节调用malloc。

删除初次通话中的malloc。

pipe->data = malloc(sizeof(char *));

奖励这将消除潜在的内存泄漏

修改

所以data是一个“动态字符串数组”

在for循环中：

pipe[i].data = malloc(sizeof(char *) * BUFFER_SIZE * chunks[i].size);

将其更改为：

pipe[i].data = malloc(sizeof(char **) * BUFFER_SIZE * chunks[i].size);

Answer 2

正如您所知，您在.modal { height: 100%; .modal-dialog { top: 50% !important; margin-top:0; margin-bottom:0; } //keep proper transitions on fade in &.fade .modal-dialog { transform: translateY(-100%) !important; } &.in .modal-dialog { transform: translateY(-50%) !important; } }和option中的struct str_list字段使用了灵活的数组。

您必须为您的结构分配占用该空间。我编译并运行了你的代码但是，我改变了：

struct pipeline

和

struct pipeline {
    char *name;
    int size;
    char **data;
    int *option; // pointer to int
};

这样做，您需要确保为此指针添加struct str_list { char *name; int size; int pipes; char **argv; int *option; // pointer to int };次调用。

malloc

我检查了您从未设置struct str_list *chunks = list_split(cmd, buffer); struct pipeline *pipe = malloc(chunks->pipes * sizeof *pipe); pipe->data = malloc(sizeof(char *)); int i = 0; for (i = 0; i < chunks->pipes; i++) { pipe[i].data = malloc(sizeof(char *) * BUFFER_SIZE * chunks[i].size); int j = 0; pipe[i].size = chunks[i].size; for (j = 0; j < chunks[i].size; j++) { if (chunks[i].argv[j] == NULL) { chunks[i].argv[j] = '\0'; break; } pipe[i].option = malloc(sizeof(int) * 10); // However many options... chunks[i].option = malloc(sizeof(int) * 10); // However many options... chunks[i].option[i] = 0; pipe[i].data[j] = strdup(chunks[i].argv[j]); pipe[i].option[0] = chunks[i].option[i];字段的util.c函数中的list_split文件，因此我明确初始化了option。

在这些更改之后，这些valgrind不再吐出那些错误，但是，你仍然会发现很多内存泄漏。

调查Valgrind无效阅读

更新/编辑

2 个答案: