I have other Inline::C modules which access libs in the exact same /usr/local/lib directory, without specifying -L, that compile fine

That's the puzzle - if you can work out why it's *only* libmpg123 that's posing the problem, then you've solved the puzzle.

As AM said, turning on BUILD_NOISY is the first thing to do - and feel free to post full output here if the cause of the problem is still not apparent to you.
Look for a warning that no library was found for -lmpg123. That would tell you that the mpg123 library was not found, and would mean that MakeMaker has removed the reference to it. Hence there would be no reference to it in the generated Makefile.

I cannot find an explanation for how the (non-)existence of a library is determined

The code that deals with this is in ExtUtils/Liblist/Kid.pm.
If that code fails to locate the library, then EU::MM deems it non-existent and removes the link

Cheers,
Rob

In reply to Re: Perplexed by Inline::C/MakeMaker LD path by syphilis
in thread Perplexed by Inline::C/MakeMaker LD path by halfcountplus

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.