Possible Memory leak while compiling.

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1

When compiling a .ll file as:

$ valgrind clang main.ll

I noticed lot of memory leaks:

==18396== HEAP SUMMARY:

==18396== in use at exit: 647,329 bytes in 619 blocks

==18396== total heap usage: 6,754 allocs, 6,135 frees, 1,571,191 bytes allocated

==18396==

==18396== LEAK SUMMARY:

==18396== definitely lost: 69,392 bytes in 4 blocks

==18396== indirectly lost: 374,050 bytes in 595 blocks

==18396== possibly lost: 12,207 bytes in 8 blocks

==18396== still reachable: 191,680 bytes in 12 blocks

==18396== suppressed: 0 bytes in 0 blocks

Is this okay ? or Known issue ?

Thanks,

Sourabh.

2

Hello Tomar,

If you look carefully at the invoked -cc1 command-line, there’s a flag -disable-free which is always passed:

$ clang-cl /c a.cpp -###

clang version 12.0.0 (https://github.com/llvm/llvm-project.git 0eab9d5823815c6520697f8d725c402c88e5d050)

Target: x86_64-pc-windows-msvc

Thread model: posix

InstalledDir: F:\llvm-project__test..\buildninjaRpMalloc2\bin

(in-process)

“F:\llvm-project\buildninjaRpMalloc2\bin\clang-cl.exe” “-cc1” “-triple” “x86_64-pc-windows-msvc19.28.29334” “-emit-obj” “-mrelax-all” “-mincremental-linker-compatible” “–mrelax-relocations” “-disable-free” “-disable-llvm-verifier” “-discard-value-names” “-main-file-name” “a.cpp” “-mrelocation-model” “pic” “-pic-level” “2” “-mframe-pointer=none” “-relaxed-aliasing” “-fmath-errno” “-fno-rounding-math” “-mconstructor-aliases” “-munwind-tables” “-target-cpu” “x86-64” “-mllvm” “-x86-asm-syntax=intel” “-tune-cpu” “generic” “-D_MT” “-flto-visibility-public-std” “–dependent-lib=libcmt” “–dependent-lib=oldnames” “-stack-protector” “2” “-fms-volatile” “-fdiagnostics-format” “msvc” “-resource-dir” “F:\llvm-project\buildninjaRpMalloc2\lib\clang\12.0.0” “-internal-isystem” “F:\llvm-project\buildninjaRpMalloc2\lib\clang\12.0.0\include” “-internal-isystem” “C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\VC\Tools\MSVC\14.28.29333\ATLMFC\include” “-internal-isystem” “C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\VC\Tools\MSVC\14.28.29333\include” “-internal-isystem” “C:\Program Files (x86)\Windows Kits\NETFXSDK\4.8\include\um” “-internal-isystem” “C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\ucrt” “-internal-isystem” “C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\shared” “-internal-isystem” “C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\um” “-internal-isystem” “C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\winrt” “-internal-isystem” “C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\cppwinrt” “-fdeprecated-macro” “-fdebug-compilation-dir” “F:\llvm-project\__test” “-ferror-limit” “19” “-fmessage-length=120” “-fno-use-cxa-atexit” “-fms-extensions” “-fms-compatibility” “-fms-compatibility-version=19.28.29334” “-std=c++14” “-fdelayed-template-parsing” “-fcolor-diagnostics” “-faddrsig” “-o” “a.obj” “-x” “c++” “a.cpp”

The purpose of the flag is to speed-up the process shutdown, by disabling heap deallocations on exit. It is used in conjunction with llvm::BuryPointer. Unless you call the -cc1 command directly or use libTooling, this flag is always active.

Alex.

3

Hi Alexandre,

I tried removing -disable-free from CLANG default commandline, but VALGRIND still reports leaks(quantitatively same as with -disable-free passed):

Summary:

with -disable-free

==22725== Command: /home/trunk/build/release/bin/clang main.c -g

==22725==

==22725==

==22725== HEAP SUMMARY:

==22725== in use at exit: 251,896 bytes in 12 blocks

==22725== total heap usage: 3,754 allocs, 3,742 frees, 734,893 bytes allocated

==22725==

==22725== LEAK SUMMARY:

==22725== definitely lost: 67,584 bytes in 1 blocks

==22725== indirectly lost: 0 bytes in 0 blocks

==22725== possibly lost: 0 bytes in 0 blocks

==22725== still reachable: 184,312 bytes in 11 blocks

==22725== suppressed: 0 bytes in 0 blocks

==22725== Rerun with --leak-check=full to see details of leaked memory

==22725==

==22725== For counts of detected and suppressed errors, rerun with: -v

==22725== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

After removing -disable-free

==22506== Command: /home/trunk/build/release/bin/clang main.c -g

==22506==

==22506==

==22506== HEAP SUMMARY:

==22506== in use at exit: 251,896 bytes in 12 blocks

==22506== total heap usage: 3,754 allocs, 3,742 frees, 734,869 bytes allocated

==22506==

==22506== LEAK SUMMARY:

==22506== definitely lost: 67,584 bytes in 1 blocks

==22506== indirectly lost: 0 bytes in 0 blocks

==22506== possibly lost: 0 bytes in 0 blocks

==22506== still reachable: 184,312 bytes in 11 blocks

==22506== suppressed: 0 bytes in 0 blocks

==22506== Rerun with --leak-check=full to see details of leaked memory

==22506==

==22506== For counts of detected and suppressed errors, rerun with: -v

==22506== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

Thanks,

Sourabh.