Perl_do_vecget(): change offset arg to STRLEN type

... and fix up its caller, pp_vec().

This is part of a fix for RT #130915.

pp_vec() is responsible for extracting out the offset and size from SVs on
the stack, and then calling do_vecget() with those values. (Sometimes the
call is done indirectly by storing the offset in the LvTARGOFF() field of
a SVt_PVLV, then later Perl_magic_getvec() passes the LvTARGOFF() value to
do_vecget().)

Now SvCUR, SvLEN and LvTARGOFF are all of type STRLEN (a.k.a Size_t),
while the offset arg of do_vecget() is of type SSize_t (i.e. there's a
signed/unsigned mismatch). It makes more sense to make the arg of type
STRLEN. So that is what this commit does.

At the same time this commit fixes up pp_vec() to handle all the
possibilities where the offset value can't fit into a STRLEN, returning 0
or croaking accordingly, so that do_vecget() is never called with a
truncated or wrapped offset.

The next commit will fix up the internals of do_vecget() and do_vecset(),
which have to worry about offset*(2^n) wrapping or being > SvCUR().

This commit is based on an earlier proposed fix by Aaron Crane.

1 files changed, 1 insertions, 1 deletions

diff --git a/embed.fnc b/embed.fnc
index 3a68a3538f..654dad9998 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -491,7 +491,7 @@ pR	|Off_t	|do_tell	|NN GV* gv
 : Defined in doop.c, used only in pp.c
 p	|I32	|do_trans	|NN SV* sv
 : Used in my.c and pp.c
-p	|UV	|do_vecget	|NN SV* sv|SSize_t offset|int size
+p	|UV	|do_vecget	|NN SV* sv|STRLEN offset|int size
 : Defined in doop.c, used only in mg.c (with /* XXX slurp this routine */)
 p	|void	|do_vecset	|NN SV* sv
 : Defined in doop.c, used only in pp.c