c - 我需要释放 ptsname() 的结果吗？

Question

当我调用 ptsname() 时，我会得到一个 char* 返回。

联机帮助页没有指定其链接、所有权或生命周期，但 valgrind 显示它导致了泄漏(使用 --leak-check=full)。

==46958== 128 bytes in 1 blocks are definitely lost in loss record 41 of 65
==46958==    at 0x10010FEBB: malloc (in /usr/local/Cellar/valgrind/3.11.0/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==46958==    by 0x1003F9682: ptsname (in /usr/lib/system/libsystem_c.dylib)
==46958==    by 0x10001BA5F: startJob(childproc*) (unix-base.cc:211)
==46958==    by 0x100019CAB: stepChild(childproc*, std::__1::function<bin::Job* (bin::Job*)>) (unix-base.cc:281)
==46958==    by 0x100018F2C: bin::runJobs(std::__1::function<bin::Job* (bin::Job*)>, int) (unix-base.cc:350)
==46958==    by 0x1000027FC: pmain() (bin.cc:65)
==46958==    by 0x100003787: main (bin.cc:90)

然而，在free()-ing结果时，我得到了通常的未malloc'd错误:

bin(46690,0x7fff76531000) malloc: *** error for object 0x7fb35af00f90: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
./bootstrap.sh: line 41: 46690 Abort trap: 6           bin/bin

这是否只是该平台上 ptsname() 内部实现的泄漏，还是我应该(以某种方式)释放结果？

Answer 1

该库分配该内存，文档称该库可能会重用该内存，因此您不应该不释放它。

On success, ptsname() returns a pointer to a string in static storage which will be overwritten by subsequent calls. This pointer must not be freed. On failure, a NULL pointer is returned.
_{The man page}

您应该忽略此 valgrind 警告。您可以告诉 valgrind 为您忽略它。

--ignore-fn=<name>
Any direct heap allocation (i.e. a call to malloc, new, etc, or a call to a function named by an --alloc-fn option) that occurs in a function specified by this option will be ignored. This is mostly useful for testing purposes. This option can be specified multiple times on the command line, to name multiple functions.
_{The man page}