From: Arnaldo Carvalho de Melo Date: Mon, 4 Feb 2019 14:04:20 +0000 (-0300) Subject: perf clang: Do not use 'return std::move(something)' X-Git-Tag: v5.0-rc6~4^2^2~5 X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=d34cecfb6b2bdc35713180ba4fcfd912a2f3e9bf;p=uclinux-h8%2Flinux.git perf clang: Do not use 'return std::move(something)' It prevents copy elision, generating this warning when building with fedora:rawhide's clang: clang version 7.0.1 (Fedora 7.0.1-2.fc30) Target: x86_64-unknown-linux-gnu Thread model: posix InstalledDir: /usr/bin Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9 Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/9 Selected GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9 Candidate multilib: .;@m64 Candidate multilib: 32;@m32 Selected multilib: .;@m64 $ make -C tools/perf CC=clang LIBCLANGLLVM=1 util/c++/clang.cpp: In function 'std::unique_ptr > perf::getBPFObjectFromModule(llvm::Module*)': util/c++/clang.cpp:163:18: error: moving a local object in a return statement prevents copy elision [-Werror=pessimizing-move] 163 | return std::move(Buffer); | ~~~~~~~~~^~~~~~~~ util/c++/clang.cpp:163:18: note: remove 'std::move' call cc1plus: all warnings being treated as errors References: http://www.cplusplus.com/forum/general/186411/#msg908572 https://en.cppreference.com/w/cpp/language/return#Notes https://en.cppreference.com/w/cpp/language/copy_elision Cc: Adrian Hunter Cc: Jiri Olsa Cc: Luis Cláudio Gonçalves Cc: Namhyung Kim Cc: Wang Nan Link: https://lkml.kernel.org/n/tip-lehqf5x5q96l0o8myhb6blz6@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/util/c++/clang.cpp b/tools/perf/util/c++/clang.cpp index 89512504551b..39c0004f2886 100644 --- a/tools/perf/util/c++/clang.cpp +++ b/tools/perf/util/c++/clang.cpp @@ -160,7 +160,7 @@ getBPFObjectFromModule(llvm::Module *Module) } PM.run(*Module); - return std::move(Buffer); + return Buffer; } }