C++ 用户泄漏，libc++；漏报或假阳性
我正在使用clang编译器和libc++标准库在mac上用C++11构建一个动态库。当我在链接到动态库的测试代码上运行valgrind时，我得到的一块内存肯定丢失了。以下是valgrind报告：C++ 用户泄漏，libc++；漏报或假阳性,c++,memory-leaks,clang,valgrind,libc++,C++,Memory Leaks,Clang,Valgrind,Libc++,我正在使用clang编译器和libc++标准库在mac上用C++11构建一个动态库。当我在链接到动态库的测试代码上运行valgrind时，我得到的一块内存肯定丢失了。以下是valgrind报告： ==45659== 36 bytes in 1 blocks are definitely lost in loss record 57 of 228 ==45659== at 0x66BB: malloc (vg_replace_malloc.c:300) ==45659== by 0x3
==45659== 36 bytes in 1 blocks are definitely lost in loss record 57 of 228
==45659== at 0x66BB: malloc (vg_replace_malloc.c:300)
==45659== by 0x31EAB0: __Balloc_D2A (in /usr/lib/system/libsystem_c.dylib)
==45659== by 0x31F2A5: __d2b_D2A (in /usr/lib/system/libsystem_c.dylib)
==45659== by 0x31BED6: __dtoa (in /usr/lib/system/libsystem_c.dylib)
==45659== by 0x3438A9: __vfprintf (in /usr/lib/system/libsystem_c.dylib)
==45659== by 0x36A2DA: __v2printf (in /usr/lib/system/libsystem_c.dylib)
==45659== by 0x34FF66: _vsnprintf (in /usr/lib/system/libsystem_c.dylib)
==45659== by 0x34FFC5: vsnprintf_l (in /usr/lib/system/libsystem_c.dylib)
==45659== by 0x34057A: snprintf_l (in /usr/lib/system/libsystem_c.dylib)
==45659== by 0x10C75A: std::__1::num_put<char, std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> > >::do_put(std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> >, std::__1::ios_base&, char, double) const (in /usr/lib/libc++.1.dylib)
==45659== by 0xF3221: std::__1::basic_ostream<char, std::__1::char_traits<char> >::operator<<(double) (in /usr/lib/libc++.1.dylib)
==45659== by 0x12102: lmpsdata::header_data::write_dimension(std::__1::basic_ofstream<char, std::__1::char_traits<char> >&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) (header_data.cpp:75)
==45659==
==45659== LEAK SUMMARY:
==45659== definitely lost: 36 bytes in 1 blocks
==45659== indirectly lost: 0 bytes in 0 blocks
==45659== possibly lost: 0 bytes in 0 blocks
==45659== still reachable: 18,340 bytes in 215 blocks
==45659== suppressed: 25,274 bytes in 374 blocks
==45659==1个块中的36个字节肯定会在228个块中的丢失记录57中丢失
==45659==0x66BB:malloc（vg_替换_malloc.c:300）
==45659==0x31EAB0:u Balloc_D2A（在/usr/lib/system/libsystem_c.dylib中）
==45659==0x31F2A5:u d2b_D2A（在/usr/lib/system/libsystem_c.dylib中）
==45659==0x31BED6:u dtoa（在/usr/lib/system/libsystem_c.dylib中）
==45659==0x3438A9:u vfprintf（在/usr/lib/system/libsystem_c.dylib中）
==45659==0x36A2DA:u v2printf（在/usr/lib/system/libsystem_c.dylib中）
==45659==0x34FF66:_vsnprintf（在/usr/lib/system/libsystem_c.dylib中）
==45659==by 0x34FFC5:vsnprintf_l（在/usr/lib/system/libsystem_c.dylib中）
==45659==by 0x34057A:snprintf_l（在/usr/lib/system/libsystem_c.dylib中）
==45659==by 0x10C75A:std:：u 1:：num_put:：do_put（std:u 1:：ostreambuf_迭代器，std:：u 1:：ios_base&，char，double）const（in/usr/lib/libc++.1.dylib）
==45659==by 0xF3221:std:：u 1:：basic_ostream:：operator您没有提到您正在使用的OSX和valgrind的确切版本。我无法在我使用的版本（OSX 10.10；valgrind HEAD==valgrind-3.11.0.SVN）上完全重现这一点
这不是在C++
标准库中，而是在C
库中。您应该能够用简单的代码复制它（几乎相同）：
#include <stdio.h>
#include <xlocale.h>
int
main(int argc, char **argv)
{
locale_t loc = newlocale(LC_NUMERIC_MASK, "C", (locale_t)0);
double d = 22.22;
char buffer[1024];
snprintf_l(buffer, 1024, loc, "%f\n", d);
printf("%s", buffer);
freelocale(loc);
}
我会对它进行压制，因为它几乎毫无疑问不是真正的泄漏，完全不受你的控制
查看已发布的文件，我看不到bug存在的位置-320和以后的版本看起来都正常；底层代码似乎在必要时进行分配和释放。不过，这个bug可能已经被引入并修复，因为我没有对所有的源代码进行彻底的搜索；有问题的文件是，您正在查看dtoaresult
assignments&frees
要确定libc的版本，可以执行以下操作：
$ otool -l /usr/lib/system/libsystem_c.dylib | grep -A5 ID_
在我的系统上，我得到输出：
cmd LC_ID_DYLIB
cmdsize 64
name /usr/lib/system/libsystem_c.dylib (offset 24)
time stamp 1 Thu Jan 1 01:00:01 1970
current version 1044.10.1
compatibility version 1.0.0
997，我认为，是小牛队（10.9）。我不知道他们是否在mavericks时间段的某个时间点引入了代码泄漏，然后修复了它-在\uvfprintf
例程中似乎没有一个代码路径在任何已发布的源代码中实际泄漏。您是否确保传递到header\u data:：write\u dimension（）
是否正确关闭并随后删除？另外，您是否尝试过拆分语句文件上述valgrind报告在ostream关闭和保持打开的情况下发生。第一次运行valgrind时，我忘了关闭溪流，我认为这就是问题所在。这个问题仍然存在，我使用的是valgrind-3.10.1。我在mavericks（10.9）中，libsystem_c.dylib的版本是997.90.3。当我在valgrind中运行代码时，我没有得到任何肯定丢失的泄漏，只有4个仍然可以访问，它们与您的相同。我认为你的权利这可能不是真正的泄密。我想知道这是否是valgrind-3.10.1和C++11的问题。valgrind 3.10.1很容易误报泄漏，因为它无法正确跟踪分配-我已经看到了其中一些，通常使用系统级抑制文件来防止报告这些泄漏。谢谢，我将研究如何设置suppression file.Pass-in--gen suppressions=yes以获得相应的抑制，并直接删除代码中的行，使其在不同代码路径下显示时更易于回收
==26151== 32 bytes in 1 blocks are still reachable in loss record 28 of 85
==26151== at 0x10000850B: malloc (in /usr/local/Cellar/valgrind/HEAD/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==26151== by 0x1002BC7DF: __Balloc_D2A (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002B9533: __rv_alloc_D2A (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002B9B3A: __dtoa (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002E1D52: __vfprintf (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x10030A9AE: __v2printf (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002EF154: _vsnprintf (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002EF1B3: vsnprintf_l (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002DF5F7: snprintf_l (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x100000ECA: main (leak.cpp:10)
==26151==
==26151== 36 bytes in 1 blocks are still reachable in loss record 30 of 85
==26151== at 0x10000850B: malloc (in /usr/local/Cellar/valgrind/HEAD/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==26151== by 0x1002BC7DF: __Balloc_D2A (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002BD055: __d2b_D2A (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002B986B: __dtoa (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002E1D52: __vfprintf (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x10030A9AE: __v2printf (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002EF154: _vsnprintf (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002EF1B3: vsnprintf_l (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002DF5F7: snprintf_l (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x100000ECA: main (leak.cpp:10)
==26151==
==26151== 80 bytes in 1 blocks are still reachable in loss record 47 of 85
==26151== at 0x10000850B: malloc (in /usr/local/Cellar/valgrind/HEAD/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==26151== by 0x1002BC736: __Balloc_D2A (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002BD055: __d2b_D2A (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002B986B: __dtoa (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002E1D52: __vfprintf (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x10030A9AE: __v2printf (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002EF154: _vsnprintf (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002EF1B3: vsnprintf_l (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x1002DF5F7: snprintf_l (in /usr/lib/system/libsystem_c.dylib)
==26151== by 0x100000ECA: main (leak.cpp:10)
$ otool -l /usr/lib/system/libsystem_c.dylib | grep -A5 ID_
cmd LC_ID_DYLIB
cmdsize 64
name /usr/lib/system/libsystem_c.dylib (offset 24)
time stamp 1 Thu Jan 1 01:00:01 1970
current version 1044.10.1
compatibility version 1.0.0