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/proto.h b/proto.h
index 3e55e21c3b..f1d6181b4b 100644
--- a/proto.h
+++ b/proto.h
@@ -806,7 +806,7 @@ PERL_CALLCONV Off_t	Perl_do_tell(pTHX_ GV* gv)
 PERL_CALLCONV I32	Perl_do_trans(pTHX_ SV* sv);
 #define PERL_ARGS_ASSERT_DO_TRANS	\
 	assert(sv)
-PERL_CALLCONV UV	Perl_do_vecget(pTHX_ SV* sv, SSize_t offset, int size);
+PERL_CALLCONV UV	Perl_do_vecget(pTHX_ SV* sv, STRLEN offset, int size);
 #define PERL_ARGS_ASSERT_DO_VECGET	\
 	assert(sv)
 PERL_CALLCONV void	Perl_do_vecset(pTHX_ SV* sv);