There is no Pg.c in the distribution, only Pg.xs, which will be translated to Pg.c by the ExtUtils/xsubpp tool in your perl distribution.

Depending on a lot of aspects, line numbers in Pg.c have no meaning to people working on different versions of perl, DBI or OS.

If you build from source, you can find the line numbers after make/nmake/dmake/gmake:

$ grep ^#line Pg.c | tail -4
#line 907 "Pg.xs"
#line 2834 "Pg.c"
#line 39 "./Pg.xsi"
#line 3359 "Pg.c"
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Only the line numbers in Pg.xs will be useful to others (using the same version of DBD::Pg).