Bug 20676 – regex backtracking memory leak

With this code: ``` import core.memory: GC; import std.regex; void f() { match("", ctRegex!(`^(?!\.)a$`)); } void main() { f(); GC.collect(); } ``` using this LDC: ``` $ ldc2 --version LDC - the LLVM D compiler (1.20.1): based on DMD v2.090.1 and LLVM 9.0.1 built with LDC - the LLVM D compiler (1.20.1) Default target: x86_64-unknown-linux-gnu Host CPU: nocona ``` valgrind reports a "definitely lost" leak: ``` $ valgrind --track-origins=yes --num-callers=50 --leak-check=full ./simple ==26749== Memcheck, a memory error detector ==26749== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==26749== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info ==26749== Command: ./simple ==26749== ==26749== Conditional jump or move depends on uninitialised value(s) ==26749== at 0x19966B: _D2gc4impl12conservativeQw3Gcx12collectRootsMFNbNlPvQcZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x17E992: _D4core6thread8osthread15scanAllTypeImplFNbMDFNbEQBvQBtQBp8ScanTypePvQcZvQgZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x17D4E8: _D4core6thread8osthread18callWithStackShellFNbMDFNbPvZvZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x17EA74: thread_scanAll (in /home/ritaka/regex-leak/simple) ==26749== by 0x19A2BD: _D2gc4impl12conservativeQw3Gcx12markParallelMFNbbZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x19633E: _D2gc4impl12conservativeQw3Gcx11fullcollectMFNbbZm (in /home/ritaka/regex-leak/simple) ==26749== by 0x197D42: _D2gc4impl12conservativeQw3Gcx10smallAllocMFNbmKmkxC8TypeInfoZPv (in /home/ritaka/regex-leak/simple) ==26749== by 0x1949EF: _D2gc4impl12conservativeQw14ConservativeGC__T9runLockedS_DQCeQCeQCcQCnQBs12mallocNoSyncMFNbmkKmxC8TypeInfoZPvS_DQEgQEgQEeQEp10mallocTimelS_DQFiQFiQFgQFr10numMallocslTmTkTmTxQCzZQFcMFNbKmKkKmKxQDsZQDl (in /home/ritaka/regex-leak/simple) ==26749== by 0x196E04: _DThn16_2gc4impl12conservativeQw14ConservativeGC6mallocMFNbmkxC8TypeInfoZPv (in /home/ritaka/regex-leak/simple) ==26749== by 0x129A46: _D3std5regex8internal12backtracking__T19BacktrackingMatcherTaTSQCjQCiQCf2ir__T5InputTaZQjZQCa10fwdMatcherMFNaNbNeKxSQEkQEjQEgQCb__T5RegexTaZQjAvZCQFoQFnQFkQFe__TQEtTaTQEbZQFd (in /home/ritaka/regex-leak/simple) ==26749== by 0x129254: _D3std5regex__T11ctRegexImplVAyaa9_5e283f215c2e296124VQzA0Z4funcFNeCQCoQCn8internal12backtracking__T19BacktrackingMatcherTaTSQEtQEsQCf2ir__T5InputTaZQjZQCaZb (in /home/ritaka/regex-leak/simple) ==26749== by 0x129B4D: _D3std5regex8internal12backtracking__T19BacktrackingMatcherTaTSQCjQCiQCf2ir__T5InputTaZQjZQCa9matchImplMFNeZi (in /home/ritaka/regex-leak/simple) ==26749== by 0x13A07B: _D3std5regex8internal12backtracking__T19BacktrackingMatcherTaTSQCjQCiQCf2ir__T5InputTaZQjZQCa5matchMFNeASQDzQDyQDvQBq__T5GroupTmZQjZi (in /home/ritaka/regex-leak/simple) ==26749== by 0x1544F1: _D3std5regex__T10RegexMatchTAyaZQr__T6__ctorTSQBsQBr__T14CTRegexWrapperTaZQtZQBoMFNcNeQCgQBsZ__T9__lambda3TASQEdQEc8internal2ir__T5GroupTmZQjZQBuMFQBoZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x153F0B: _D3std5regex8internal2ir__T15SmallFixedArrayTSQBsQBrQBoQBi__T5GroupTmZQjVki3ZQBy6mutateMFMDFAQBwZvZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x153DBC: _D3std5regex__T10RegexMatchTAyaZQr__T6__ctorTSQBsQBr__T14CTRegexWrapperTaZQtZQBoMFNcNeQCgQBsZSQDoQDn__TQDkTQDbZQDs (in /home/ritaka/regex-leak/simple) ==26749== by 0x128F41: _D3std5regex__T5matchTAyaTSQzQx__T14CTRegexWrapperTaZQtZQBpFNfQBoQBnZSQCqQCp__T10RegexMatchTQCsZQr (in /home/ritaka/regex-leak/simple) ==26749== by 0x128E95: _D6simple1fFZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x128FA8: _Dmain (in /home/ritaka/regex-leak/simple) ==26749== by 0x183D2F: _D2rt6dmain212_d_run_main2UAAamPUQgZiZ6runAllMFZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x183C1E: _d_run_main2 (in /home/ritaka/regex-leak/simple) ==26749== by 0x183A7D: _d_run_main (in /home/ritaka/regex-leak/simple) ==26749== by 0x153C34: main (in /home/ritaka/regex-leak/simple) ==26749== Uninitialised value was created by a stack allocation ==26749== at 0x17EA40: thread_scanAll (in /home/ritaka/regex-leak/simple) ==26749== ==26749== ==26749== HEAP SUMMARY: ==26749== in use at exit: 82,040 bytes in 4 blocks ==26749== total heap usage: 558 allocs, 554 frees, 351,784 bytes allocated ==26749== ==26749== 32 bytes in 1 blocks are possibly lost in loss record 2 of 4 ==26749== at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==26749== by 0x193C3A: _D2gc4impl12conservativeQw10initializeFZC4coreQBs11gcinterface2GC (in /home/ritaka/regex-leak/simple) ==26749== by 0x191569: _D4core2gc8registry16createGCInstanceFAyaZCQBpQBn11gcinterface2GC (in /home/ritaka/regex-leak/simple) ==26749== by 0x17F2CC: gc_init (in /home/ritaka/regex-leak/simple) ==26749== by 0x17F355: gc_init_nothrow (in /home/ritaka/regex-leak/simple) ==26749== by 0x19C8C0: _DThn16_2gc4impl5protoQo7ProtoGC6mallocMFNbmkxC8TypeInfoZPv (in /home/ritaka/regex-leak/simple) ==26749== by 0x129A46: _D3std5regex8internal12backtracking__T19BacktrackingMatcherTaTSQCjQCiQCf2ir__T5InputTaZQjZQCa10fwdMatcherMFNaNbNeKxSQEkQEjQEgQCb__T5RegexTaZQjAvZCQFoQFnQFkQFe__TQEtTaTQEbZQFd (in /home/ritaka/regex-leak/simple) ==26749== by 0x129254: _D3std5regex__T11ctRegexImplVAyaa9_5e283f215c2e296124VQzA0Z4funcFNeCQCoQCn8internal12backtracking__T19BacktrackingMatcherTaTSQEtQEsQCf2ir__T5InputTaZQjZQCaZb (in /home/ritaka/regex-leak/simple) ==26749== by 0x129B4D: _D3std5regex8internal12backtracking__T19BacktrackingMatcherTaTSQCjQCiQCf2ir__T5InputTaZQjZQCa9matchImplMFNeZi (in /home/ritaka/regex-leak/simple) ==26749== by 0x13A07B: _D3std5regex8internal12backtracking__T19BacktrackingMatcherTaTSQCjQCiQCf2ir__T5InputTaZQjZQCa5matchMFNeASQDzQDyQDvQBq__T5GroupTmZQjZi (in /home/ritaka/regex-leak/simple) ==26749== by 0x1544F1: _D3std5regex__T10RegexMatchTAyaZQr__T6__ctorTSQBsQBr__T14CTRegexWrapperTaZQtZQBoMFNcNeQCgQBsZ__T9__lambda3TASQEdQEc8internal2ir__T5GroupTmZQjZQBuMFQBoZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x153F0B: _D3std5regex8internal2ir__T15SmallFixedArrayTSQBsQBrQBoQBi__T5GroupTmZQjVki3ZQBy6mutateMFMDFAQBwZvZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x153DBC: _D3std5regex__T10RegexMatchTAyaZQr__T6__ctorTSQBsQBr__T14CTRegexWrapperTaZQtZQBoMFNcNeQCgQBsZSQDoQDn__TQDkTQDbZQDs (in /home/ritaka/regex-leak/simple) ==26749== by 0x128F41: _D3std5regex__T5matchTAyaTSQzQx__T14CTRegexWrapperTaZQtZQBpFNfQBoQBnZSQCqQCp__T10RegexMatchTQCsZQr (in /home/ritaka/regex-leak/simple) ==26749== by 0x128E95: _D6simple1fFZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x128FA8: _Dmain (in /home/ritaka/regex-leak/simple) ==26749== by 0x183D2F: _D2rt6dmain212_d_run_main2UAAamPUQgZiZ6runAllMFZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x183C1E: _d_run_main2 (in /home/ritaka/regex-leak/simple) ==26749== by 0x183A7D: _d_run_main (in /home/ritaka/regex-leak/simple) ==26749== by 0x153C34: main (in /home/ritaka/regex-leak/simple) ==26749== ==26749== 81,936 bytes in 1 blocks are definitely lost in loss record 4 of 4 ==26749== at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==26749== by 0x1291F4: _D3std5regex__T11ctRegexImplVAyaa9_5e283f215c2e296124VQzA0Z4funcFNeCQCoQCn8internal12backtracking__T19BacktrackingMatcherTaTSQEtQEsQCf2ir__T5InputTaZQjZQCaZb (in /home/ritaka/regex-leak/simple) ==26749== by 0x129B4D: _D3std5regex8internal12backtracking__T19BacktrackingMatcherTaTSQCjQCiQCf2ir__T5InputTaZQjZQCa9matchImplMFNeZi (in /home/ritaka/regex-leak/simple) ==26749== by 0x13A07B: _D3std5regex8internal12backtracking__T19BacktrackingMatcherTaTSQCjQCiQCf2ir__T5InputTaZQjZQCa5matchMFNeASQDzQDyQDvQBq__T5GroupTmZQjZi (in /home/ritaka/regex-leak/simple) ==26749== by 0x1544F1: _D3std5regex__T10RegexMatchTAyaZQr__T6__ctorTSQBsQBr__T14CTRegexWrapperTaZQtZQBoMFNcNeQCgQBsZ__T9__lambda3TASQEdQEc8internal2ir__T5GroupTmZQjZQBuMFQBoZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x153F0B: _D3std5regex8internal2ir__T15SmallFixedArrayTSQBsQBrQBoQBi__T5GroupTmZQjVki3ZQBy6mutateMFMDFAQBwZvZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x153DBC: _D3std5regex__T10RegexMatchTAyaZQr__T6__ctorTSQBsQBr__T14CTRegexWrapperTaZQtZQBoMFNcNeQCgQBsZSQDoQDn__TQDkTQDbZQDs (in /home/ritaka/regex-leak/simple) ==26749== by 0x128F41: _D3std5regex__T5matchTAyaTSQzQx__T14CTRegexWrapperTaZQtZQBpFNfQBoQBnZSQCqQCp__T10RegexMatchTQCsZQr (in /home/ritaka/regex-leak/simple) ==26749== by 0x128E95: _D6simple1fFZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x128FA8: _Dmain (in /home/ritaka/regex-leak/simple) ==26749== by 0x183D2F: _D2rt6dmain212_d_run_main2UAAamPUQgZiZ6runAllMFZv (in /home/ritaka/regex-leak/simple) ==26749== by 0x183C1E: _d_run_main2 (in /home/ritaka/regex-leak/simple) ==26749== by 0x183A7D: _d_run_main (in /home/ritaka/regex-leak/simple) ==26749== by 0x153C34: main (in /home/ritaka/regex-leak/simple) ==26749== ==26749== LEAK SUMMARY: ==26749== definitely lost: 81,936 bytes in 1 blocks ==26749== indirectly lost: 0 bytes in 0 blocks ==26749== possibly lost: 32 bytes in 1 blocks ==26749== still reachable: 72 bytes in 2 blocks ==26749== suppressed: 0 bytes in 0 blocks ==26749== Reachable blocks (those to which a pointer was found) are not shown. ==26749== To see them, rerun with: --leak-check=full --show-leak-kinds=all ==26749== ==26749== For counts of detected and suppressed errors, rerun with: -v ==26749== ERROR SUMMARY: 473 errors from 3 contexts (suppressed: 0 from 0) ``` Is this is a bug in the regex library?

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