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Fix -Wcast-function-type warnings

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Three groups of issues needed to be addressed:

load_external_function() and related functions returned PGFunction,
even though not necessarily all callers are looking for a function of
type PGFunction.  Since these functions are really just wrappers
around dlsym(), change to return void * just like dlsym().

In dynahash.c, we are using strlcpy() where a function with a
signature like memcpy() is expected.  This should be safe, as the new
comment there explains, but the cast needs to be augmented to avoid
the warning.

In PL/Python, methods all need to be cast to PyCFunction, per Python
API, but this now runs afoul of these warnings.  (This issue also
exists in core CPython.)

To fix the second and third case, we add a new type pg_funcptr_t that
is defined specifically so that gcc accepts it as a special function
pointer that can be cast to any other function pointer without the
warning.

Also add -Wcast-function-type to the standard warning flags, subject
to configure check.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/1e97628e-6447-b4fd-e230-d109cec2d584%402ndquadrant.com
This commit is contained in:
Peter Eisentraut
2020-07-14 19:36:30 +02:00
parent 101f903e51
commit de8feb1f3a
7 changed files with 127 additions and 18 deletions
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11
src/backend/utils/hash/dynahash.c
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@@ -398,7 +398,16 @@ hash_create(const char *tabname, long nelem, HASHCTL *info, int flags)
if (flags & HASH_KEYCOPY)
hashp->keycopy = info->keycopy;
else if (hashp->hash == string_hash)
hashp->keycopy = (HashCopyFunc) strlcpy;
{
/*
* The signature of keycopy is meant for memcpy(), which returns
* void*, but strlcpy() returns size_t. Since we never use the return
* value of keycopy, and size_t is pretty much always the same size as
* void *, this should be safe. The extra cast in the middle is to
* avoid warnings from -Wcast-function-type.
*/
hashp->keycopy = (HashCopyFunc) (pg_funcptr_t) strlcpy;
}
else
hashp->keycopy = memcpy;