strdup against array? segfaults

Does anyone see a problem with my code? attempting to do a strdup is failing with a segmentation fault within libc

plugintools.h

Code:

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/* Provide function for adding files to be copied/linked
  into report
*/
typedef struct file_list {
  int count;
  char **filepath;
} file_list;

// max path length for any file/dir listing
#define MAXPATHLEN 1024
file_list *
add_copy_spec(const char *path);

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plugintools.c

Code:

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/* add file specification (dir, file, shell glob)
 */
file_list *
add_copy_spec(const char *path)
{
    int err, i;
    char *abspath[MAXPATHLEN];
    glob_t globbuf;

    struct file_list *fl = malloc(sizeof(file_list));
   
    err = glob(path, GLOB_DOOFFS | GLOB_APPEND, NULL, &globbuf);
    if (err) {
        fl->count = 0;
        fl->filepath = NULL;
        return fl;
    }
   
    fl->count = globbuf.gl_pathc;
    fl->filepath = malloc(sizeof(char *) * fl->count);
    // loop through our file list, append to struct array
    printf("\nfilepath loop\n");
    for (i = 0; i < globbuf.gl_pathc; i++) {
        printf("%s\n", globbuf.gl_pathv[i]);
        fl->filepath[i] = strdup(globbuf.gl_pathv[i]);

/*
        if((realpath(globbuf.gl_pathv[i], abspath)) != NULL) {
            //fl->filepath[i] = strdup(abspath);
          } else {
            continue;
        }
*/
    }
    globfree(&globbuf);
    return fl;
}

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I don't see why abspath should be a string. Did you mean

Code:

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char abspath[MAXPATHLEN]

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instead?

Quote:

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Originally Posted by tabstop

I don't see why abspath should be a string. Did you mean

Code:

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char abspath[MAXPATHLEN]

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instead?

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Code:

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fl->filepath[i] = strdup(globbuf.gl_pathv[i]);

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Using the updated code, however produces:

Code:

---

file_list *
add_copy_spec(const char *path)
{
    int err, i;
    char abspath[MAXPATHLEN];
    glob_t globbuf;

    struct file_list *fl = malloc(sizeof(file_list));
   
    err = glob(path, GLOB_DOOFFS | GLOB_APPEND, NULL, &globbuf);
    if (err) {
        fl->count = 0;
        fl->filepath = NULL;
        return fl;
    }
   
    fl->count = globbuf.gl_pathc;
    fl->filepath = malloc(sizeof(char *) * fl->count);
    // loop through our file list, append to struct array
    printf("\nfilepath loop\n");
    for (i = 0; i < globbuf.gl_pathc; i++) {
        if((realpath(globbuf.gl_pathv[i], abspath)) != NULL) {
            fl->filepath[i] = strdup(abspath);
          } else {
            continue;
        }
    }
    globfree(&globbuf);
    return fl;
}

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Code:

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make  check-TESTS
make[2]: Entering directory `/home/uzr/Code/jibbajabba/c/sos/tests'
Running suite(s): SOS
__Creating hardlink blank_file_for_tests -> /tmp/sos_tests/blank_file_for_tests
__Creating symlink /home/uzr/Code/jibbajabba/c/sos/tests/blank_file_for_tests -> /tmp/sos_tests/blank_file_for_tests
*** glibc detected *** /home/uzr/Code/jibbajabba/c/sos/tests/.libs/lt-check_sos: realloc(): invalid pointer: 0x00007f2f2a284508 ***
======= Backtrace: =========
/lib64/libc.so.6[0x30fce74a76]
/lib64/libc.so.6(realloc+0x2e2)[0x30fce7a472]
/lib64/libc.so.6[0x30fcea77cf]
/lib64/libc.so.6(glob64+0xecc)[0x30fcea8a0c]
/home/uzr/Code/jibbajabba/c/sos/libsos/.libs/libsos.so.0(add_copy_spec+0x4f)[0x7f2f2a284b8f]
/home/uzr/Code/jibbajabba/c/sos/tests/.libs/lt-check_sos[0x400ed2]
/usr/lib64/libcheck.so.0(srunner_run_all+0x6e8)[0x7f2f2a06dbb8]
/home/uzr/Code/jibbajabba/c/sos/tests/.libs/lt-check_sos[0x400e7b]
/lib64/libc.so.6(__libc_start_main+0xfd)[0x30fce1eb1d]
/home/uzr/Code/jibbajabba/c/sos/tests/.libs/lt-check_sos[0x400cd9]
======= Memory map: ========
00400000-00402000 r-xp 00000000 fd:00 1704636                            /home/uzr/Code/jibbajabba/c/sos/tests/.libs/lt-check_sos
00601000-00602000 rw-p 00001000 fd:00 1704636                            /home/uzr/Code/jibbajabba/c/sos/tests/.libs/lt-check_sos
01d8a000-01dab000 rw-p 00000000 00:00 0                                  [heap]
30fc800000-30fc81e000 r-xp 00000000 fd:00 205589                        /lib64/ld-2.11.1.so
30fca1d000-30fca1e000 r--p 0001d000 fd:00 205589                        /lib64/ld-2.11.1.so
30fca1e000-30fca1f000 rw-p 0001e000 fd:00 205589                        /lib64/ld-2.11.1.so
30fca1f000-30fca20000 rw-p 00000000 00:00 0
30fce00000-30fcf6f000 r-xp 00000000 fd:00 205590                        /lib64/libc-2.11.1.so
30fcf6f000-30fd16f000 ---p 0016f000 fd:00 205590                        /lib64/libc-2.11.1.so
30fd16f000-30fd173000 r--p 0016f000 fd:00 205590                        /lib64/libc-2.11.1.so
30fd173000-30fd174000 rw-p 00173000 fd:00 205590                        /lib64/libc-2.11.1.so
30fd174000-30fd179000 rw-p 00000000 00:00 0
30fd600000-30fd617000 r-xp 00000000 fd:00 205596                        /lib64/libpthread-2.11.1.so
30fd617000-30fd816000 ---p 00017000 fd:00 205596                        /lib64/libpthread-2.11.1.so
30fd816000-30fd817000 r--p 00016000 fd:00 205596                        /lib64/libpthread-2.11.1.so
30fd817000-30fd818000 rw-p 00017000 fd:00 205596                        /lib64/libpthread-2.11.1.so
30fd818000-30fd81c000 rw-p 00000000 00:00 0
3109e00000-3109e16000 r-xp 00000000 fd:00 205627                        /lib64/libgcc_s-4.4.3-20100127.so.1
3109e16000-310a015000 ---p 00016000 fd:00 205627                        /lib64/libgcc_s-4.4.3-20100127.so.1
310a015000-310a016000 rw-p 00015000 fd:00 205627                        /lib64/libgcc_s-4.4.3-20100127.so.1
7f2f2a066000-7f2f2a069000 rw-p 00000000 00:00 0
7f2f2a069000-7f2f2a070000 r-xp 00000000 fd:00 271395                    /usr/lib64/libcheck.so.0.0.0
7f2f2a070000-7f2f2a26f000 ---p 00007000 fd:00 271395                    /usr/lib64/libcheck.so.0.0.0
7f2f2a26f000-7f2f2a270000 rw-p 00006000 fd:00 271395                    /usr/lib64/libcheck.so.0.0.0
7f2f2a270000-7f2f2a271000 rw-p 00000000 00:00 0
7f2f2a282000-7f2f2a284000 rw-p 00000000 00:00 0
7f2f2a284000-7f2f2a286000 r-xp 00000000 fd:00 1704627                    /home/uzr/Code/jibbajabba/c/sos/libsos/.libs/libsos.so.0.1.5
7f2f2a286000-7f2f2a485000 ---p 00002000 fd:00 1704627                    /home/uzr/Code/jibbajabba/c/sos/libsos/.libs/libsos.so.0.1.5
7f2f2a485000-7f2f2a486000 rw-p 00001000 fd:00 1704627                    /home/uzr/Code/jibbajabba/c/sos/libsos/.libs/libsos.so.0.1.5
7f2f2a486000-7f2f2a487000 rw-p 00000000 00:00 0
7fffc3ca3000-7fffc3cb8000 rw-p 00000000 00:00 0                          [stack]
7fffc3dff000-7fffc3e00000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
66%: Checks: 3, Failures: 0, Errors: 1
check_sos.c:78:E:Core:test_copy_spec:0: (after this point) Received signal 6 (Aborted)
FAIL: check_sos

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Interestingly enough this works:

Code:

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

void
print_struct_files()
{
    char *data = malloc(sizeof(char) * 100);
    char **files = malloc(100);
    int i;
    for(i = 0; i < 5; i++) {
        files[i] = strdup("Testing");
        printf("%s\n", files[i]);
    }
}

void
main()
{
    printf("WORKING\n");
    print_struct_files();
}

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i was under the impression that strdup would handle malloc'ing

Quote:

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Originally Posted by schurt

i was under the impression that strdup would handle malloc'ing

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It should.

attempting to access memory at

Code:

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fl->filepath = malloc(sizeof(char *) * fl->count);

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fl->filepath[2] return invalid address.

if fl->count returns 39 why isn't my array being created correctly?

Code:

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fl->filepath = malloc(sizeof(char *) * fl->count);

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You are asking for fl-> count char pointers. Is this really correct? This is why the recommendation to use sizeof on an expression, and not a type, is made.

fl->filepath = malloc(sizeof(*(fl->filepath)) * fl->count);

Quote:

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Originally Posted by whiteflags

Code:

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fl->filepath = malloc(sizeof(char *) * fl->count);

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You are asking for fl-> count char pointers. Is this really correct? This is why the recommendation to use sizeof on an expression, and not a type, is made.

fl->filepath = malloc(sizeof(*(fl->filepath)) * fl->count);

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You are correct and I am going to alter my code to reflect the expression and not the type

I fixed the code with this result:

Code:

---

/* add file specification (dir, file, shell glob)
 */
file_list *
add_copy_spec(const char *path)
{
    int err, i;
    char abspath[MAXPATHLEN];
    glob_t globbuf;

    struct file_list *fl = malloc(sizeof(file_list));
   
    memset(&globbuf, 0, sizeof(globbuf));
    err = glob(path, 0, NULL, &globbuf);
    if (err) {
        fl->count = 0;
        fl->filepath = NULL;
        return fl;
    }
   
    fl->count = globbuf.gl_pathc;
    fl->filepath = malloc(sizeof(*(fl->filepath)) * fl->count);
    // loop through our file list, append to struct array
    printf("\nfilepath loop\n");
    for (i = 0; i < globbuf.gl_pathc; i++) {
        if((realpath(globbuf.gl_pathv[i], abspath)) != NULL) {
            fl->filepath[i] = strdup(abspath);
            printf("fpath: %s\n", fl->filepath[i]);
          } else {
            continue;
        }
    }
    globfree(&globbuf);
    return fl;
}

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How many other malloc calls are there in the program, that you haven't shown us?

This is cause and effect. You're posting the effect, or where you think the problem is.
Except it isn't in all likelyhood a problem at all.

Put add_copy_spec() in a separate file, and a MINIMAL main() to call it - does it crash?
My guess is that it doesn't. But if it does, you have a really good example to post.

Now, back to the cause.
The grim reality of C memory management (there isn't any) is that ANY screwup you make can have any one of these outcomes
- instant death
- death in an unrelated part of the program
- absolutely nothing happens

What to do:
Run the program in the debugger (compile with -g), and linked against electric fence
If it's an overrun, it will trap and drop you in the debugger at the line of code which stepped off memory it didn't allocate.

Run the program under valgrind - see the manual for more details.

Quote:

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Originally Posted by Salem

How many other malloc calls are there in the program, that you haven't shown us?

This is cause and effect. You're posting the effect, or where you think the problem is.
Except it isn't in all likelyhood a problem at all.


Put add_copy_spec() in a separate file, and a MINIMAL main() to call it - does it crash?
My guess is that it doesn't. But if it does, you have a really good example to post.

Now, back to the cause.
The grim reality of C memory management (there isn't any) is that ANY screwup you make can have any one of these outcomes
- instant death
- death in an unrelated part of the program
- absolutely nothing happens

What to do:
Run the program in the debugger (compile with -g), and linked against electric fence
If it's an overrun, it will trap and drop you in the debugger at the line of code which stepped off memory it didn't allocate.

Run the program under valgrind - see the manual for more details.

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Those 2 mallocs are the only calls in the entire library, ill look into electric fence thanks for the tip