C - 大输入时的内存泄漏
C - memory leak in case of big input
对于作业，我必须订购一份学生名单。每个人都由一个数字（大小为 15 的字符串）、他父亲的姓氏（字符串 20）、他母亲的姓氏（字符串 20）和他的名字（字符串 20）表示。
我做了一个程序，它从一个文件构建学生列表并对其进行排序（我使用合并排序来这样做）。
当我 运行 小部分学生（<10 000）的程序一切正常（根据 valgrind 没有内存泄漏或任何东西）。
但是，当我尝试在更大的（超过 100 000）上使用它时，我得到了分段错误 11。我调查了 Valgrind，它说错误来自 strcy 或 strcasecmp 函数，并且渲染：
==2433== Invalid write of size 8
==2433== at 0x4019BD: merge (sort.c:59)
==2433== by 0x40173B: sortBeginEnd (sort.c:38)
==2433== by 0x4014B0: sortWithoutInterval (sort.c:9)
==2433== by 0x401EE0: firstSort (sort.c:166)
==2433== by 0x4009EB: main (main.c:44)
==2433== Address 0xffe79ac88 is on thread 1's stack
==2433==
==2433==
==2433== Process terminating with default action of signal 11 (SIGSEGV)
==2433== Access not within mapped region at address 0xFFE79AC88
==2433== at 0x4019BD: merge (sort.c:59)
==2433== If you believe this happened as a result of a stack
==2433== overflow in your program's main thread (unlikely but
==2433== possible), you can try to increase the size of the
==2433== main thread stack using the --main-stacksize= flag.
==2433== The main thread stack size used in this run was 8388608.
==2433==
==2433== Process terminating with default action of signal 11 (SIGSEGV)
==2433== Access not within mapped region at address 0xFFE79AC81
==2433== at 0x4A256B0: _vgnU_freeres (in /usr/lib/valgrind/vgpreload_core-amd64-linux.so)
==2433== If you believe this happened as a result of a stack
==2433== overflow in your program's main thread (unlikely but
==2433== possible), you can try to increase the size of the
==2433== main thread stack using the --main-stacksize= flag.
==2433== The main thread stack size used in this run was 8388608.
==2433==
==2433== HEAP SUMMARY:
==2433== in use at exit: 12,800,101 bytes in 500,007 blocks
==2433== total heap usage: 500,008 allocs, 1 frees, 12,800,669 bytes allocated
==2433==
==2433== LEAK SUMMARY:
==2433== definitely lost: 0 bytes in 0 blocks
==2433== indirectly lost: 0 bytes in 0 blocks
==2433== possibly lost: 0 bytes in 0 blocks
==2433== still reachable: 12,800,101 bytes in 500,007 blocks
==2433== suppressed: 0 bytes in 0 blocks
==2433== Rerun with --leak-check=full to see details of leaked memory
==2433==
==2433== For counts of detected and suppressed errors, rerun with: -v
==2433== ERROR SUMMARY: 7452721 errors from 31 contexts (suppressed: 0 from 0)
错误可能是我使用了太多内存（每个学生代表 79 个字符 = 316 字节，我有 100 000 个字符，所以如果我是对的，它是 31 600 000 字节）？
PS : 我对栈和堆的概念不是很熟悉
编辑：
"Everything is fine" valgrind 报告：
==2454==
==2454== HEAP SUMMARY:
==2454== in use at exit: 0 bytes in 0 blocks
==2454== total heap usage: 50,008 allocs, 50,008 frees, 1,280,669 bytes allocated
==2454==
==2454== All heap blocks were freed -- no leaks are possible
==2454==
==2454== For counts of detected and suppressed errors, rerun with: -v
==2454== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
编辑2：
代码可用here如果你想检查它。
最后编辑：
感谢@Lundin 的回答，我终于找到了解决方案。问题是我没有使用 malloc 为 mergeSort 的合并部分分配临时数组。
我会再调查一下 heap/stack 的问题，以完全理解这个问题。
堆栈是您的函数保存其 local/temporary 数据（参数和局部变量）的地方。它被组织成一堆纸，所以当你调用一个函数时，参数被放入堆栈，当函数完成时，除了结果之外的所有东西都被从堆栈中丢弃。通常堆栈的大小有限。
堆是内存，您分配的数据保存在其中 (f.e.malloc())。你可以有不同的堆（对于你的应用程序，对于每个进程和系统范围）
你甚至没有提到这是针对哪个系统的。由于 Valgrind，我假设 Linux。你没有提到你在哪里分配变量。显然不在堆上，因为 Valgrid 在那里只报告 12.8kb。
如果我没记错的话（我对 Linux 知之甚少）进程的堆栈大小大约为 8Mb。
316 * 10000 = 3.16 Mb.
316 * 100000 = 31.60 Mb.
合格的猜测：如果您使用 malloc 以外的任何其他方式分配变量，那么堆栈溢出就是所描述问题的根源。
只要在程序中使用大量内存，就必须在堆上动态分配它们。
对于作业，我必须订购一份学生名单。每个人都由一个数字（大小为 15 的字符串）、他父亲的姓氏（字符串 20）、他母亲的姓氏（字符串 20）和他的名字（字符串 20）表示。
我做了一个程序，它从一个文件构建学生列表并对其进行排序（我使用合并排序来这样做）。
当我 运行 小部分学生（<10 000）的程序一切正常（根据 valgrind 没有内存泄漏或任何东西）。
但是，当我尝试在更大的（超过 100 000）上使用它时，我得到了分段错误 11。我调查了 Valgrind，它说错误来自 strcy 或 strcasecmp 函数，并且渲染：
==2433== Invalid write of size 8
==2433== at 0x4019BD: merge (sort.c:59)
==2433== by 0x40173B: sortBeginEnd (sort.c:38)
==2433== by 0x4014B0: sortWithoutInterval (sort.c:9)
==2433== by 0x401EE0: firstSort (sort.c:166)
==2433== by 0x4009EB: main (main.c:44)
==2433== Address 0xffe79ac88 is on thread 1's stack
==2433==
==2433==
==2433== Process terminating with default action of signal 11 (SIGSEGV)
==2433== Access not within mapped region at address 0xFFE79AC88
==2433== at 0x4019BD: merge (sort.c:59)
==2433== If you believe this happened as a result of a stack
==2433== overflow in your program's main thread (unlikely but
==2433== possible), you can try to increase the size of the
==2433== main thread stack using the --main-stacksize= flag.
==2433== The main thread stack size used in this run was 8388608.
==2433==
==2433== Process terminating with default action of signal 11 (SIGSEGV)
==2433== Access not within mapped region at address 0xFFE79AC81
==2433== at 0x4A256B0: _vgnU_freeres (in /usr/lib/valgrind/vgpreload_core-amd64-linux.so)
==2433== If you believe this happened as a result of a stack
==2433== overflow in your program's main thread (unlikely but
==2433== possible), you can try to increase the size of the
==2433== main thread stack using the --main-stacksize= flag.
==2433== The main thread stack size used in this run was 8388608.
==2433==
==2433== HEAP SUMMARY:
==2433== in use at exit: 12,800,101 bytes in 500,007 blocks
==2433== total heap usage: 500,008 allocs, 1 frees, 12,800,669 bytes allocated
==2433==
==2433== LEAK SUMMARY:
==2433== definitely lost: 0 bytes in 0 blocks
==2433== indirectly lost: 0 bytes in 0 blocks
==2433== possibly lost: 0 bytes in 0 blocks
==2433== still reachable: 12,800,101 bytes in 500,007 blocks
==2433== suppressed: 0 bytes in 0 blocks
==2433== Rerun with --leak-check=full to see details of leaked memory
==2433==
==2433== For counts of detected and suppressed errors, rerun with: -v
==2433== ERROR SUMMARY: 7452721 errors from 31 contexts (suppressed: 0 from 0)
错误可能是我使用了太多内存（每个学生代表 79 个字符 = 316 字节，我有 100 000 个字符，所以如果我是对的，它是 31 600 000 字节）？
PS : 我对栈和堆的概念不是很熟悉
编辑：
"Everything is fine" valgrind 报告：
==2454==
==2454== HEAP SUMMARY:
==2454== in use at exit: 0 bytes in 0 blocks
==2454== total heap usage: 50,008 allocs, 50,008 frees, 1,280,669 bytes allocated
==2454==
==2454== All heap blocks were freed -- no leaks are possible
==2454==
==2454== For counts of detected and suppressed errors, rerun with: -v
==2454== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
编辑2：
代码可用here如果你想检查它。
最后编辑：
感谢@Lundin 的回答，我终于找到了解决方案。问题是我没有使用 malloc 为 mergeSort 的合并部分分配临时数组。
我会再调查一下 heap/stack 的问题，以完全理解这个问题。
堆栈是您的函数保存其 local/temporary 数据（参数和局部变量）的地方。它被组织成一堆纸，所以当你调用一个函数时，参数被放入堆栈，当函数完成时，除了结果之外的所有东西都被从堆栈中丢弃。通常堆栈的大小有限。
堆是内存，您分配的数据保存在其中 (f.e.malloc())。你可以有不同的堆（对于你的应用程序，对于每个进程和系统范围）
你甚至没有提到这是针对哪个系统的。由于 Valgrind，我假设 Linux。你没有提到你在哪里分配变量。显然不在堆上，因为 Valgrid 在那里只报告 12.8kb。
如果我没记错的话（我对 Linux 知之甚少）进程的堆栈大小大约为 8Mb。
316 * 10000 = 3.16 Mb.
316 * 100000 = 31.60 Mb.
合格的猜测：如果您使用 malloc 以外的任何其他方式分配变量，那么堆栈溢出就是所描述问题的根源。
只要在程序中使用大量内存，就必须在堆上动态分配它们。