On Monday, 5 November 2018 11:33:58 PST René J.V. Bertin wrote: > On Monday November 05 2018 12:03:31 René J.V. Bertin wrote: > >In my experience clang generates significantly more compact binaries > > Quite: bzipped tarballs of everything except the examples, translations, > QWE, QtWebView and Qt3D:
Off-topic: no one uses bzip2 anymore. It's slow to compress, slow to decompress and produces worse results than xz. > -rw-r--r-- 1 root root 363M Sep 8 13:22 > qt5-kde-devel-5.9.6.linux_3.x86_64.tbz2 (1003Mb uncompressed tarball) > -rw-r--r-- 1 root root 199M Nov 5 19:22 > qt5-kde-devel-5.9.7.linux_3.x86_64.tbz2 (710Mb uncompressed tarball) > > The first built with GCC 8, the 2nd with clang 6.0; identical compiler > options (release build, -O3, force_debug_info for qtbase). Please compare debug-stripped binaries. text data bss dec hex filename 7205857 200632 1714 7408203 710a4b lib/libQt5Widgets.so 6727027 197920 1576 6926523 69b0bb clang/libQt5Widgets.so Both are -O3 -march=native -g1 builds. So yes, the Clang build is smaller, but not significantly so. And since -O3 means "aggressively optimise, even if it takes longer to compile or increases the size considerably", you don't really care about size. Bigger code could indicate more optimisations applied (loop unrolling, vectorisation). Anyway, compare the debug sections of the two: GCC: Section Headers: [Nr] Name Type Off Size ES Flags Lk Inf Al [29] .debug_line PROGBITS 00710a80 002c360b 0 0 0 1 [30] .debug_info PROGBITS 009d408b 00567018 0 0 0 1 [31] .debug_abbrev PROGBITS 00f3b0a3 0002813a 0 0 0 1 [32] .debug_aranges PROGBITS 00f631e0 0000fd70 0 0 0 16 [33] .debug_str PROGBITS 00f72f50 001f84b5 1 MS 0 0 1 [34] .debug_ranges PROGBITS 0116b410 002f3a20 0 0 0 16 Clang: [28] .debug_aranges PROGBITS 0069c0a0 00000080 0 0 0 16 [29] .debug_info PROGBITS 0069c120 004b52fc 0 0 0 1 [30] .debug_abbrev PROGBITS 00b5141c 00006dea 0 0 0 1 [31] .debug_line PROGBITS 00b58206 0032d586 0 0 0 1 [32] .debug_str PROGBITS 00e8578c 000377fb 1 MS 0 0 1 [33] .debug_macinfo PROGBITS 00ebcf87 000000b6 0 0 0 1 [34] .debug_ranges PROGBITS 00ebd040 00135ff0 0 0 0 16 Clang carries 9793421 bytes of debug information, while GCC produces 13951906. That's a much bigger difference. -- Thiago Macieira - thiago.macieira (AT) intel.com Software Architect - Intel Open Source Technology Center _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
