malloc()在以下代码中给了我一个错误。我用了valgrind，但仍然没有效果。我是C语言的初学者，我的队友和我试图实现SHA1算法，但有些东西我们都无法理解，并且花了几个小时在这上面。这是有错误的函数-
/*
* Returns an array of chunks on the heap from the message
*/
static unsigned char **sha1_chunkify(const unsigned char *message, const uint64_t message_length)
{
long num_chunks = message_length / 64; //breaking it down into 64 byte chunks
printf("%lu %ldn", message_length, num_chunks);
unsigned char **chunks = malloc (num_chunks * sizeof(*chunks)); //Error is coming over here
for (int i = 0; i < num_chunks; i++) {
chunks[i] = malloc (64 * sizeof(*chunks[i])); //Or sometimes over here.
for (int j = 0; j < 64; j++) {
chunks[i][j] = message[64 * i + j];
}
}
return chunks;
}
下面是gdb在这些行的输出-
117 printf("%lu %ldn", message_length, num_chunks);
(gdb)
1472 23
118 unsigned char **chunks = (unsigned char **) malloc (num_chunks * sizeof(*chunks));
(gdb)
*** Error in `/home/username/Desktop/Project_VCS/a.out': malloc(): memory corruption: 0x000000000060cac0 ***
Program received signal SIGABRT, Aborted.
0x00007ffff7a4bcc9 in __GI_raise (sig=sig@entry=6)
at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
56 ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory.
和Valgrind显示如下-
3
mytry.c
==16688== Invalid write of size 1
==16688== at 0x401EA6: append_zeroes (sha1.c:155)
==16688== by 0x401F1D: sha1_pad (sha1.c:177)
==16688== by 0x401FB7: sha1 (sha1.c:200)
==16688== by 0x400C72: snap_file (snap.c:40)
==16688== by 0x4012F7: snap (snap.c:143)
==16688== by 0x401852: snap_all (snap.c:220)
==16688== by 0x40222E: main (nako.c:24)
==16688== Address 0x5220720 is 0 bytes after a block of size 1,408 alloc'd
==16688== at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==16688== by 0x401F7B: sha1 (sha1.c:195)
==16688== by 0x400C72: snap_file (snap.c:40)
==16688== by 0x4012F7: snap (snap.c:143)
==16688== by 0x401852: snap_all (snap.c:220)
==16688== by 0x40222E: main (nako.c:24)
==16688==
==16688== Invalid write of size 1
==16688== at 0x401E6A: append_msg_len (sha1.c:142)
==16688== by 0x401F34: sha1_pad (sha1.c:179)
==16688== by 0x401FB7: sha1 (sha1.c:200)
==16688== by 0x400C72: snap_file (snap.c:40)
==16688== by 0x4012F7: snap (snap.c:143)
==16688== by 0x401852: snap_all (snap.c:220)
==16688== by 0x40222E: main (nako.c:24)
==16688== Address 0x5220758 is not stack'd, malloc'd or (recently) free'd
==16688==
1472 23
valgrind: m_mallocfree.c:277 (mk_plain_bszB): Assertion 'bszB != 0' failed.
valgrind: This is probably caused by your program erroneously writing past the
end of a heap block and corrupting heap metadata. If you fix any
invalid writes reported by Memcheck, this assertion failure will
probably go away. Please try that before reporting this as a bug.
==16688== at 0x38050BAC: ??? (in /usr/lib/valgrind/memcheck-amd64-linux)
==16688== by 0x38050D06: ??? (in /usr/lib/valgrind/memcheck-amd64-linux)
==16688== by 0x3805B36A: ??? (in /usr/lib/valgrind/memcheck-amd64-linux)
==16688== by 0x3805D2D7: ??? (in /usr/lib/valgrind/memcheck-amd64-linux)
==16688== by 0x380216D4: ??? (in /usr/lib/valgrind/memcheck-amd64-linux)
==16688== by 0x380218A2: ??? (in /usr/lib/valgrind/memcheck-amd64-linux)
==16688== by 0x3809DC03: ??? (in /usr/lib/valgrind/memcheck-amd64-linux)
==16688== by 0x380AC87C: ??? (in /usr/lib/valgrind/memcheck-amd64-linux)
sched status:
running_tid=1
Thread 1: status = VgTs_Runnable
==16688== at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==16688== by 0x401D94: sha1_chunkify (sha1.c:118)
==16688== by 0x401FCA: sha1 (sha1.c:202)
==16688== by 0x400C72: snap_file (snap.c:40)
==16688== by 0x4012F7: snap (snap.c:143)
==16688== by 0x401852: snap_all (snap.c:220)
==16688== by 0x40222E: main (nako.c:24)
我已经检查了几个线程，但错误仍然存在。如果以前有人问过这个问题，我很抱歉。我找不到相同的。提前感谢您。
函数append_zero和append_msg_len -
/*
* Pad the message with its length.
* The input lengths are in bytes, while the padding, in accordance with
* the SHA1 algorithm, is done in bits.
*/
static inline void append_msg_len(unsigned char *message,
uint64_t *message_length,
uint64_t original_msglen)
{
int shift = 56;
while (shift >= 0) {
/* Add the next 8 bits. */
message[*message_length] = (8 * original_msglen >> shift) & 0xff;
shift -= 8;
*message_length += 1;
}
}
/*
* Appends enough zeroes until the message has just enough room for appending
* the message length, i.e, length 448 mod 512
*/
static inline void append_zeroes(unsigned char *message, uint64_t *message_length)
{
while (*message_length % 64 != 56) {
message[*message_length] = (unsigned char) 0x00;
*message_length += 1;
}
}
看看下面的代码:
long num_chunks = message_length / 64; //breaking it down into 64 byte chunks
例如，如果我们使用message_length = 63, num_chunks变为零，这显然是错误的。如果你使用
long num_chunks = (message_length + 63) / 64; //breaking it down into 64 byte chunks
您将获得正确数量的块，并且希望您的其余代码将表现良好。