But now I'm puzzled as to the output we get for printf("***%s***\n", MY_FORMAT); The quotes either side of %.17e are apparently missing from MY_FORMAT. So how does printf(MY_FORMAT, sqrt(2.0)) even compile ?

C syntax and preprocessing rules. MY_FORMAT is substituted by the C preprocessor, so the compiler sees printf("***%s***\n", "%.17e");, strips the quotes off of the string constant like any other, and the output is ***%.17e*** if everything works correctly. The % character is also special in the DOS shell, which uses it for variable substitution: %PATH% on DOS is $PATH on *nix. The trailing % is required, but I would not be surprised if bugs in the shell like to eat random % characters.

You will be much better off passing a number instead of a string constant if you want this to compile on Windows.

In reply to Re^7: Defining an XS symbol in the Makefile.PL (quoting) by jcb
in thread Defining an XS symbol in the Makefile.PL by syphilis

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.