对于getpwnam中的内存泄漏，是否有修复方法或解决方法

Is there a fix or a workaround for the memory leak in getpwnam?

本文关键字：方法 是否 解决 getpwnam 内存 泄漏 对于      更新时间：2023-10-16

getpwnam内存泄漏有修复方法或解决方法吗？

getpwnam()不会发生内存泄漏。实际上，后续调用将覆盖其静态内部缓冲区。

相反，这类函数是不可重入的，因此是非线程安全的

也就是说，内存泄漏是由那些系统调用引起的，这些系统调用通过malloc()分配内存，并在返回的数据使用后让应用程序对free()负责。

在这些情况下，RAII习惯用法是可取的，以免忘记释放分配的内存——请参阅异常安全。std::tr1::shared_ptr<>也是一种可行的方式：对于shared_ptr，必须向free()提供一个自定义的deleter，即当shared_ptr超出范围时的原始指针。

在这种观点下，一些危险的函数是scandir()、asprintf()、vasprintf()等。

使用getpwnam_r。

我认为没有解决办法。以上答案没有帮助，请参阅：

daniel@senap:~/dev/tryouts$ uname -a
Linux senap 3.2.0-24-generic #39-Ubuntu SMP Mon May 21 16:52:17 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
daniel@senap:~/dev/tryouts$ cat getpwnam-leak.c 
#include <sys/types.h>
#include <pwd.h>
extern void __libc_freeres(void);
int main()
{
  char buf[1024];
  struct passwd pw, *result;
  getpwnam_r("root", &pw, buf, sizeof(buf), &result);
  __libc_freeres();
}
daniel@senap:~/dev/tryouts$ valgrind --leak-check=full ./getpwnam-leak
==6951== Memcheck, a memory error detector
==6951== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==6951== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==6951== Command: ./getpwnam-leak
==6951== 
==6951== 
==6951== HEAP SUMMARY:
==6951==     in use at exit: 300 bytes in 11 blocks
==6951==   total heap usage: 69 allocs, 58 frees, 9,234 bytes allocated
==6951== 
==6951== 300 (60 direct, 240 indirect) bytes in 1 blocks are definitely lost in loss record 11 of 11
==6951==    at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) 
==6951==    by 0x4F35D94: nss_parse_service_list (nsswitch.c:678)
==6951==    by 0x4F36855: __nss_database_lookup (nsswitch.c:175)
==6951==    by 0x55F32A4: ???
==6951==    by 0x4EEF1AC: getpwnam_r@@GLIBC_2.2.5 (getXXbyYY_r.c:256)
==6951==    by 0x400607: main (in /home/daniel/dev/tryouts/getpwnam-leak)
==6951== 
==6951== LEAK SUMMARY:
==6951==    definitely lost: 60 bytes in 1 blocks
==6951==    indirectly lost: 240 bytes in 10 blocks
==6951==      possibly lost: 0 bytes in 0 blocks
==6951==    still reachable: 0 bytes in 0 blocks
==6951==         suppressed: 0 bytes in 0 blocks
==6951== 
==6951== For counts of detected and suppressed errors, rerun with: -v
==6951== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 2 from 2)
daniel@senap:~/dev/tryouts$

要修复此问题，只需执行以下操作：

sudo sed -i s/compat/files/g /etc/nsswitch.conf

这似乎是由于libnss_compat中的一个错误引起的。更多信息，请访问bugs.debian.org.

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