Fix some cases of indirectly casting away const.

Newest versions of gcc are able to detect cases where code implicitly
casts away const by assigning the result of strchr() or a similar
function applied to a "const char *" value to a target variable
that's just "char *".  This of course creates a hazard of not getting
a compiler warning about scribbling on a string one was not supposed
to, so fixing up such cases is good.

This patch fixes a dozen or so places where we were doing that.
Most are trivial additions of "const" to the target variable,
since no actually-hazardous change was occurring.  There is one
place in ecpg.trailer where we were indeed violating the intention
of not modifying a string passed in as "const char *".  I believe
that's harmless not a live bug, but let's fix it by copying the
string before modifying it.

There is a remaining trouble spot in ecpg/preproc/variable.c,
which requires more complex surgery.  I've left that out of this
commit because I want to study that code a bit more first.

We probably will want to back-patch this once compilers that detect
this pattern get into wider circulation, but for now I'm just
going to apply it to master to see what the buildfarm says.

Thanks to Bertrand Drouvot for finding a couple more spots than
I had.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Discussion: https://postgr.es/m/1324889.1764886170@sss.pgh.pa.us

1 files changed, 1 insertions, 1 deletions

diff --git a/src/backend/utils/adt/xid8funcs.c b/src/backend/utils/adt/xid8funcs.c
index a211a107767..4b3f7a69b3b 100644
--- a/src/backend/utils/adt/xid8funcs.c
+++ b/src/backend/utils/adt/xid8funcs.c
@@ -194,7 +194,7 @@ is_visible_fxid(FullTransactionId value, const pg_snapshot *snap)
 #ifdef USE_BSEARCH_IF_NXIP_GREATER
 	else if (snap->nxip > USE_BSEARCH_IF_NXIP_GREATER)
 	{
-		void	   *res;
+		const void *res;
 
 		res = bsearch(&value, snap->xip, snap->nxip, sizeof(FullTransactionId),
 					  cmp_fxid);