Calling function in inlined C library

Question

I'm trying to make a simple wrapper around the CommonMark C library using Inline::C. I have installed libcmark.so in /usr/local/lib/.

My current code looks like this:

package Text::CommonMark;

use strict;
use warnings;

sub commonmarker {
    my $text = shift;
    return commonmark_to_html($text);
}

use Inline C => qq{

    char* commonmark_to_html(char* thetext) {

        char* result = cmark_markdown_to_html(thetext, strlen(thetext));
        return result;
    }
} => LIBS => '-L/usr/local/lib/ -llibcmark.so';

1;

When using commonmarker from a script I get:

perl: symbol lookup error: /home/erik/sublimeworks/dists/Text-CommonMark/_Inline/lib/auto/Text/CommonMark_33fb/CommonMark_33fb.so: undefined symbol: cmark_markdown_to_html

I assume that my call to cmark_markdown_to_html doesn't match its signature, but all signatures for cmark_markdown_to_html that I've found look like this:

char *cmark_markdown_to_html(const char *text, int len)

I haven't touched either C or Inline::C before so I'm probably missing something.

Answer 1

No mentioned of LIBS in the docs. The option is named libs.

use Inline C => config => libs => '-L/usr/local/lib/ -llibcmark.so';
use Inline C => <<'__EOC__';

    char* commonmark_to_html(char* thetext) {
        char* result = cmark_markdown_to_html(thetext, strlen(thetext));
        return result;
    }

__EOC__

---

Note that using char* thetext as an argument to an XS function is a sure sign of a bug. That gives you a pointer to the string buffer without telling you the format of the buffer.

Assuming the library accepts and returns text encoded using UTF-8,

SV* commonmark_to_html(SV* text_sv) {
    STRLEN text_len;
    const char* text = SvPVutf8(text_sv, text_len);
    const char* html = cmark_markdown_to_html(text, text_len);
    SV* html_sv = newSVpvn_flags(html, strlen(html), SVf_UTF8);
    free(html);
    return html_sv;
}

Optimized slightly (since having newSVpvn_flags mortalize the scalar is more efficient that having the typemap-generated code call sv_2mortal):

void commonmark_to_html(SV* text_sv) {
    STRLEN text_len;
    const char* text = SvPVutf8(text_sv, text_len);
    const char* html = cmark_markdown_to_html(text, text_len);
    SV* html_sv = newSVpvn_flags(html, strlen(html), SVf_UTF8|SVs_TEMP);
    free(html);
    ST(0) = html_sv;
    XSRETURN(1);
}

Answer 2

Your -l argument looks suspect. Usually the compiler/linker will prefix the "lib" and suffix the ".so", so normally you should just need to supply

-lcmark