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Re^3: PDL 2.058 released

by etj (Chaplain)
on Nov 08, 2021 at 15:49 UTC ( #11138578=note: print w/replies, xml ) Need Help??

in reply to Re^2: PDL 2.058 released
in thread PDL 2.058 released

Unfortunately the line numbers are a bit misleading, and the error is nothing to do with %extra etc. The error is actually happening on a call to log10() when passed a PDL_Byte (unsigned char) and I think PDL_Ushort (unsigned short). I believe it's a compiler/libc bug of some sort.

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Re^4: PDL 2.058 released
by etj (Chaplain) on Nov 08, 2021 at 23:10 UTC
    In fact, it's due to a new-ish change in GCC-land; on some versions, tgmath (type-generic maths) works fine for log10, but it seems they've changed that. Furthermore, clog10 (the complex version) is actually a GNU extension rather than part of C99, so I've adjusted ops.pd accordingly (and if there's no clog10 available, you can't do log10 on complex numbers, sorry - but it was ever thus).

    I've just released PDL 2.060 which I believe fixes this, so please give it a try.

      2.060 tests fine - but I don't know precisely what it was that changed from the earlier versions of gcc/runtime in relation to log10 - nor whether it was a change for the best, or a bug.
      Do you have a simple C script that demonstrates this change ?
      Mingw's complex.h includes clog10() beginning with Strawberry's release of perl-5.30.0 (gcc-8.3.0, runtime 6.0), so it should be available to these Windows builds, and onwards.

        Earlier GCC, this worked and produced the results you'd expect if (like previous me) you didn't properly understand the C99 tgmath, which then stopped working with more recent GCC:
        #include <tgmath.h>
        void main() {
        complex double z = 1.0;
        z = log10(z);
        printf("%f%+fi\n", creal(z), cimag(z));
        See for more. Note log10 is in the "real-only" section; GCC incorporated it into their "real or imag" tgmath for a while incorporating their own clog10 extension, but then evidently changed their minds. The presence or absence of clog10 is not relevant to log10 working or not with tgmath.
Re^4: PDL 2.058 released
by etj (Chaplain) on Nov 08, 2021 at 17:15 UTC
    I'm sure it's a compiler/libc bug, but the good news is I'm now able to reproduce it locally, so a fix should be available in due course.

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