この問題に関するさまざまなバグ ノートとスタック オーバーフローの質問 (ここにリンク) を調べましたが、まだ理解できません:
問題のあるブロックのメモリを解放するような方法で C++ コードを書くことは可能ですか?
valgrind faq は次のように述べています。
GCC を使用すると、メモリ キャッシングをグローバルに無効にすることで、STL に malloc を使用させ、できるだけ早くメモリを解放させることができます。注意してください！これを行うと、おそらくプログラムが遅くなり、場合によっては大幅に遅くなります。
GCC 2.91、2.95、3.0、および 3.1 では、-D__USE_MALLOC を指定した STL を使用してすべてのソースをコンパイルします。注意してください！これは、バージョン 3.3 以降の GCC から削除されました。
GCC 3.2.2 以降では、プログラムを実行する前に環境変数 GLIBCPP_FORCE_NEW をエクスポートする必要があります。
GCC 3.4 以降では、その変数の名前が GLIBCXX_FORCE_NEW に変更されました。
私はc9.ioアカデミックな課題の C++ ワークベンチとして使用し、以下を使用してコンパイルしています。
g++ -Wall -Wvla -Werror -g -D_GLIBCXX_DEBUG -std=c++11
c9 の gcc バージョンは次のとおりです。gcc version 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04.1)
悲しいことに、提案された微調整を理解することになると、私は途方に暮れています。これをプロジェクトに追加するにはどうすればよいですか?
これが唯一の可能な解決策ではない場合、他に何かありますか?
完全な valgrind 出力:
Press [Enter] key to start memory check of test executable...
valgrind --leak-check=full --show-leak-kinds=all -v ./MyLinkedListTest
==4729== Memcheck, a memory error detector
==4729== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==4729== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==4729== Command: ./MyLinkedListTest
==4729==
--4729-- Valgrind options:
--4729-- --leak-check=full
--4729-- --show-leak-kinds=all
--4729-- -v
--4729-- Contents of /proc/version:
--4729-- Linux version 4.2.0-c9 (root@11aafb97cfeb) (gcc version 4.9.2 (Debian 4.9.2-10) ) #1 SMP Fri Nov 20 14:49:01 UTC 2015
--4729-- Arch and hwcaps: AMD64, LittleEndian, amd64-cx16-lzcnt-rdtscp-sse3-avx-avx2-bmi
--4729-- Page sizes: currently 4096, max supported 4096
--4729-- Valgrind library directory: /usr/lib/valgrind
--4729-- Reading syms from /home/ubuntu/workspace/MyLinkedListTest
--4729-- Reading syms from /lib/x86_64-linux-gnu/ld-2.19.so
--4729-- Considering /lib/x86_64-linux-gnu/ld-2.19.so ..
--4729-- .. CRC mismatch (computed ef2bc4a1 wanted 12987a55)
--4729-- Considering /usr/lib/debug/lib/x86_64-linux-gnu/ld-2.19.so ..
--4729-- .. CRC is valid
--4729-- Reading syms from /usr/lib/valgrind/memcheck-amd64-linux
--4729-- Considering /usr/lib/valgrind/memcheck-amd64-linux ..
--4729-- .. CRC mismatch (computed 4f1eed43 wanted a323a3ab)
--4729-- object doesn't have a symbol table
--4729-- object doesn't have a dynamic symbol table
--4729-- Scheduler: using generic scheduler lock implementation.
--4729-- Reading suppressions file: /usr/lib/valgrind/default.supp
==4729== embedded gdbserver: reading from /tmp/vgdb-pipe-from-vgdb-to-4729-by-ubuntu-on-???
==4729== embedded gdbserver: writing to /tmp/vgdb-pipe-to-vgdb-from-4729-by-ubuntu-on-???
==4729== embedded gdbserver: shared mem /tmp/vgdb-pipe-shared-mem-vgdb-4729-by-ubuntu-on-???
==4729==
==4729== TO CONTROL THIS PROCESS USING vgdb (which you probably
==4729== don't want to do, unless you know exactly what you're doing,
==4729== or are doing some strange experiment):
==4729== /usr/lib/valgrind/../../bin/vgdb --pid=4729 ...command...
==4729==
==4729== TO DEBUG THIS PROCESS USING GDB: start GDB like this
==4729== /path/to/gdb ./MyLinkedListTest
==4729== and then give GDB the following command
==4729== target remote | /usr/lib/valgrind/../../bin/vgdb --pid=4729
==4729== --pid is optional if only one valgrind process is running
==4729==
--4729-- REDIR: 0x4019ca0 (ld-linux-x86-64.so.2:strlen) redirected to 0x380764b1 (???)
--4729-- Reading syms from /usr/lib/valgrind/vgpreload_core-amd64-linux.so
--4729-- Considering /usr/lib/valgrind/vgpreload_core-amd64-linux.so ..
--4729-- .. CRC mismatch (computed fc68135e wanted 45f5e986)
--4729-- object doesn't have a symbol table
--4729-- Reading syms from /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so
--4729-- Considering /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so ..
--4729-- .. CRC mismatch (computed ae683f7e wanted 08c06df2)
--4729-- object doesn't have a symbol table
==4729== WARNING: new redirection conflicts with existing -- ignoring it
--4729-- old: 0x04019ca0 (strlen ) R-> (0000.0) 0x380764b1 ???
--4729-- new: 0x04019ca0 (strlen ) R-> (2007.0) 0x04c2e1a0 strlen
--4729-- REDIR: 0x4019a50 (ld-linux-x86-64.so.2:index) redirected to 0x4c2dd50 (index)
--4729-- REDIR: 0x4019c70 (ld-linux-x86-64.so.2:strcmp) redirected to 0x4c2f2f0 (strcmp)
--4729-- REDIR: 0x401a9c0 (ld-linux-x86-64.so.2:mempcpy) redirected to 0x4c31da0 (mempcpy)
--4729-- Reading syms from /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.21
--4729-- Considering /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.21 ..
--4729-- .. CRC mismatch (computed bb97d222 wanted 173a3577)
--4729-- object doesn't have a symbol table
--4729-- Reading syms from /lib/x86_64-linux-gnu/libgcc_s.so.1
--4729-- Considering /lib/x86_64-linux-gnu/libgcc_s.so.1 ..
--4729-- .. CRC mismatch (computed f2c4ceb3 wanted bf2e028d)
--4729-- object doesn't have a symbol table
--4729-- Reading syms from /lib/x86_64-linux-gnu/libpthread-2.19.so
--4729-- Considering /lib/x86_64-linux-gnu/libpthread-2.19.so ..
--4729-- .. CRC mismatch (computed 4841b2fb wanted eec353ab)
--4729-- Considering /usr/lib/debug/lib/x86_64-linux-gnu/libpthread-2.19.so ..
--4729-- .. CRC is valid
--4729-- Reading syms from /lib/x86_64-linux-gnu/libc-2.19.so
--4729-- Considering /lib/x86_64-linux-gnu/libc-2.19.so ..
--4729-- .. CRC mismatch (computed 600bae51 wanted b4d0580d)
--4729-- Considering /usr/lib/debug/lib/x86_64-linux-gnu/libc-2.19.so ..
--4729-- .. CRC is valid
--4729-- Reading syms from /lib/x86_64-linux-gnu/libm-2.19.so
--4729-- Considering /lib/x86_64-linux-gnu/libm-2.19.so ..
--4729-- .. CRC mismatch (computed 0fbb5cf0 wanted cac31e3b)
--4729-- Considering /usr/lib/debug/lib/x86_64-linux-gnu/libm-2.19.so ..
--4729-- .. CRC is valid
--4729-- REDIR: 0x5605d60 (libc.so.6:strcasecmp) redirected to 0x4a25720 (_vgnU_ifunc_wrapper)
--4729-- REDIR: 0x5608050 (libc.so.6:strncasecmp) redirected to 0x4a25720 (_vgnU_ifunc_wrapper)
--4729-- REDIR: 0x5605530 (libc.so.6:memcpy@GLIBC_2.2.5) redirected to 0x4a25720 (_vgnU_ifunc_wrapper)
--4729-- REDIR: 0x56037c0 (libc.so.6:rindex) redirected to 0x4c2da30 (rindex)
--4729-- REDIR: 0x55fb750 (libc.so.6:malloc) redirected to 0x4c2ab10 (malloc)
--4729-- REDIR: 0x5601ac0 (libc.so.6:strlen) redirected to 0x4c2e0e0 (strlen)
--4729-- REDIR: 0x5604fa0 (libc.so.6:__GI_memcmp) redirected to 0x4c30b80 (__GI_memcmp)
--4729-- REDIR: 0x5600070 (libc.so.6:strcmp) redirected to 0x4a25720 (_vgnU_ifunc_wrapper)
--4729-- REDIR: 0x56b9200 (libc.so.6:__strcmp_ssse3) redirected to 0x4c2f1b0 (strcmp)
--4729-- REDIR: 0x4e9ee50 (libstdc++.so.6:operator new(unsigned long)) redirected to 0x4c2b070 (operator new(unsigned long))
--4729-- REDIR: 0x560a730 (libc.so.6:memcpy@@GLIBC_2.14) redirected to 0x4a25720 (_vgnU_ifunc_wrapper)
--4729-- REDIR: 0x5610fd0 (libc.so.6:__memcpy_sse2_unaligned) redirected to 0x4c2f6b0 (memcpy@@GLIBC_2.14)
--4729-- REDIR: 0x4e9ef00 (libstdc++.so.6:operator new[](unsigned long)) redirected to 0x4c2b790 (operator new[](unsigned long))
--4729-- REDIR: 0x56055c0 (libc.so.6:memset) redirected to 0x4c31350 (memset)
--4729-- REDIR: 0x4e9d0a0 (libstdc++.so.6:operator delete[](void*)) redirected to 0x4c2c7d0 (operator delete[](void*))
--4729-- REDIR: 0x55ffe20 (libc.so.6:index) redirected to 0x4a25720 (_vgnU_ifunc_wrapper)
--4729-- REDIR: 0x55ffe50 (libc.so.6:__GI_strchr) redirected to 0x4c2db90 (__GI_strchr)
--4729-- REDIR: 0x56c9090 (libc.so.6:__memmove_ssse3_back) redirected to 0x4c2f450 (memcpy@GLIBC_2.2.5)
--4729-- REDIR: 0x4e9d070 (libstdc++.so.6:operator delete(void*)) redirected to 0x4c2c250 (operator delete(void*))
--4729-- REDIR: 0x55fbdf0 (libc.so.6:free) redirected to 0x4c2bd80 (free)
==4729==
==4729== HEAP SUMMARY:
==4729== in use at exit: 72,704 bytes in 1 blocks
==4729== total heap usage: 260 allocs, 259 frees, 122,246 bytes allocated
==4729==
==4729== Searching for pointers to 1 not-freed blocks
==4729== Checked 139,240 bytes
==4729==
==4729== 72,704 bytes in 1 blocks are still reachable in loss record 1 of 1
==4729== at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4729== by 0x4E9B2AF: ??? (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.21)
==4729== by 0x4010139: call_init.part.0 (dl-init.c:78)
==4729== by 0x4010222: call_init (dl-init.c:36)
==4729== by 0x4010222: _dl_init (dl-init.c:126)
==4729== by 0x4001309: ??? (in /lib/x86_64-linux-gnu/ld-2.19.so)
==4729==
==4729== LEAK SUMMARY:
==4729== definitely lost: 0 bytes in 0 blocks
==4729== indirectly lost: 0 bytes in 0 blocks
==4729== possibly lost: 0 bytes in 0 blocks
==4729== still reachable: 72,704 bytes in 1 blocks
==4729== suppressed: 0 bytes in 0 blocks
==4729==
==4729== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
==4729== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)