[LLVMbugs] [Bug 17703] New: ninja is 11% slower when built with libc++ (compared to libstdc++)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17703

            Bug ID: 17703
           Summary: ninja is 11% slower when built with libc++ (compared
                    to libstdc++)
           Product: libc++
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: hhinnant at apple.com
          Reporter: nicolasweber at gmx.de
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Repro:

1. Build ninja ( http://martine.github.io/ninja/ )
  mkdir ~/src
  cd ~/src
  git clone git://github.com/martine/ninja.git
  cd ninja && python bootstrap.py
2. Check out chromium
  git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
  export PATH=$HOME/src/depot_tools:$PATH
  fetch chromium --nosvn=True
3. Build it with the ninja binary from step 1
  cd src
  GYP_GENERATORS=ninja build/gyp_chromium
  time caffeinate ~/src/ninja/ninja -C out/Release chrome
4. Measure empty build time of chrome:
  time caffeinate ~/src/ninja/ninja -C out/Release chrome
5. Edit ~/src/ninja/build/ninja and add "-stdlib=libstdc++" to cflags and
ldflgs, return `./ninja` to recompile ninja. (libc++ is the default in Xcode5's
clang)
6. Repeat 4. with the new binary

Expected: ninja is fast in the default build configuration.
Actual: ninja is considerably faster when built with libstdc++.

On my system, it's ~650ms vs ~720ms (min of several runs each).

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