[cfe-dev] Clang on Windows targteing gcc compiles very slowly

Edward Diener eldlistmailingz at tropicsoft.com
Fri May 29 19:08:13 PDT 2015

On 5/29/2015 9:35 PM, Justin Bogner wrote:
> On Friday, May 29, 2015, Edward Diener
> <eldlistmailingz at tropicsoft.com
> <mailto:eldlistmailingz at tropicsoft.com>> wrote:
>     I test Boost libraries mostly on Windows using various version of
>     gcc 4.3 and up, VC++ 8.0 and up, and the latest version of clang
>     which I build from source using mingw/gcc-4.8.1 in release mode.
>     While clang is a great compiler when it comes to testing code,
>     getting intelligent error message, and implementing the latest C++
>     standard, it is noticably slower ( 2x or 3x at minimum ) than the
>     other compilers I use.
>     The clang command line parameters usually being used are usually
>     along the lines of:
>     -c -x c++ -O0 -g -fno-inline -Wall -g -march=i686 -m32
>     with the addition of 'std=c++11' occasionally depending on the test.
>     Does anybody have any idea why clang is so much slower than any of
>     the other compilers I use ? It does not seem to matter whether it is
>     in C++03 mode or C++11 mode, it is noticeably slower than the other
>     compilers.
> How are you building clang? I suspect that you're using a debug build of
> clang, which is quite slow.

"which I build from source using mingw/gcc-4.8.1 in release mode."

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