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  • Bug#1067907: flam3-genome segfaults on ppc64el with -ffast-math enabled

    From Peter Blackman@21:1/5 to Trupti on Thu Jul 31 19:40:02 2025
    XPost: linux.debian.ports.powerpc

    This is a multi-part message in MIME format.
    On 30/07/2025 21:05, Trupti wrote:

    I tried multiple approaches and found that reducing the optimization level from -O3 to -O2,-O1 does not resolve the segmentation faults.

    However, when I removed only the -ffast-math flag (while keeping other optimizations) from Makefile.am, the program ran consistently without any segmentation faults.

    This seems to indicate that the instability is likely related to the -ffast-math flag, rather than the optimization level itself.


    Interesting! I was not expecting -ffast-math to be the cause of the trouble.

    Attaching a rules file to use clang. (Clang seems to break dwz!)

    If you are happy to try this, it would show if the problem is with gcc.
    If the build works with clang with -ffast-math enabled,
    I will raise a bug against gcc for this.

    Cheers,
    Peter
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  • From Peter Blackman@21:1/5 to Trupti on Fri Aug 1 12:40:01 2025
    XPost: linux.debian.ports.powerpc

    This is a multi-part message in MIME format.
    On 01/08/2025 08:17, Trupti wrote:

    .... Any additional insights or suggestions are most welcome.


    Hi Trupti,

    Just to be sure this is not an own goal,
    I attach a series file that comments out
    all the non essential patches.


    From the gcc man page, -ffast-math enables the following optimisations

    -fno-math-errno
    -funsafe-math-optimizations
    -ffinite-math-only
    -fno-rounding-math
    -fno-signaling-nans
    -fcx-limited-range
    -fexcess-precision=fast

    Maybe enable individually or as groups to determine
    which triggers the segfault?


    Best regards,
    Peter
    IzAwMS1tYW5wYWdlX3doYXRpc19maXgucGF0Y2gKMDAyLWxpYnhtbC5wYXRjaAojMDAzLWxq cGVnLnBhdGNoCjAwNC1mbGFtMy5wYXRjaAojMDA1LXJlYWRtZS5wYXRjaAojMDA2LWljdTY3 LnBhdGNoCiMwMDctYXV0b2NvbmYucGF0Y2gKIzAwOC1zdHJpbmdvcC10cnVuY2F0aW9uLnBh dGNoCiMwMDktZGVmYXVsdHMucGF0Y2gK

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