[英]Is there a fix or a workaround for the memory leak in getpwnam?
getpwnam中的内存泄漏是否有修复程序或解决方法?
getpwnam()
不会遭受内存泄漏。 实际上,后续调用将覆盖其静态内部缓冲区。
这类函数是不可重入的 ,因此是非线程安全的 。 Paul建议使用可重入版本getpwnam_r()
,可以安全地在多线程上下文中使用。
就是说,内存泄漏是由那些通过malloc()
分配内存并让应用程序负责一旦返回的数据已使用就free()
内存的系统调用引起的。
在这些情况下,建议使用RAII习惯用法,以免忘记释放分配的内存-请参阅异常安全性。 std::tr1::shared_ptr<>
也是可行的方法:对于shared_ptr,必须提供一个自定义删除器,以便在shared_ptr超出范围时free()
原始指针。
从这个角度来看,一些危险的函数是scandir()
, asprintf()
, vasprintf()
等。
使用getpwnam_r。
我认为没有解决方法。 上面的答案无济于事,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$
要解决此问题,请执行以下操作:
sudo sed -i s/compat/files/g /etc/nsswitch.conf
看来这是由于libnss_compat中的错误引起的。 有关更多信息,请访问bugs.debian.org 。
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