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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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91
configure vendored
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@ -5643,6 +5643,97 @@ if test x"$pgac_cv_prog_CXX_cxxflags__Wimplicit_fallthrough_3" = x"yes"; then
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CC} supports -Wcast-function-type, for CFLAGS" >&5
$as_echo_n "checking whether ${CC} supports -Wcast-function-type, for CFLAGS... " >&6; }
if ${pgac_cv_prog_CC_cflags__Wcast_function_type+:} false; then :
$as_echo_n "(cached) " >&6
else
pgac_save_CFLAGS=$CFLAGS
pgac_save_CC=$CC
CC=${CC}
CFLAGS="${CFLAGS} -Wcast-function-type"
ac_save_c_werror_flag=$ac_c_werror_flag
ac_c_werror_flag=yes
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
int
main ()
{
;
return 0;
}
_ACEOF
if ac_fn_c_try_compile "$LINENO"; then :
pgac_cv_prog_CC_cflags__Wcast_function_type=yes
else
pgac_cv_prog_CC_cflags__Wcast_function_type=no
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
ac_c_werror_flag=$ac_save_c_werror_flag
CFLAGS="$pgac_save_CFLAGS"
CC="$pgac_save_CC"
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CC_cflags__Wcast_function_type" >&5
$as_echo "$pgac_cv_prog_CC_cflags__Wcast_function_type" >&6; }
if test x"$pgac_cv_prog_CC_cflags__Wcast_function_type" = x"yes"; then
CFLAGS="${CFLAGS} -Wcast-function-type"
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CXX} supports -Wcast-function-type, for CXXFLAGS" >&5
$as_echo_n "checking whether ${CXX} supports -Wcast-function-type, for CXXFLAGS... " >&6; }
if ${pgac_cv_prog_CXX_cxxflags__Wcast_function_type+:} false; then :
$as_echo_n "(cached) " >&6
else
pgac_save_CXXFLAGS=$CXXFLAGS
pgac_save_CXX=$CXX
CXX=${CXX}
CXXFLAGS="${CXXFLAGS} -Wcast-function-type"
ac_save_cxx_werror_flag=$ac_cxx_werror_flag
ac_cxx_werror_flag=yes
ac_ext=cpp
ac_cpp='$CXXCPP $CPPFLAGS'
ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
int
main ()
{
;
return 0;
}
_ACEOF
if ac_fn_cxx_try_compile "$LINENO"; then :
pgac_cv_prog_CXX_cxxflags__Wcast_function_type=yes
else
pgac_cv_prog_CXX_cxxflags__Wcast_function_type=no
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
ac_ext=c
ac_cpp='$CPP $CPPFLAGS'
ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
ac_compiler_gnu=$ac_cv_c_compiler_gnu
ac_cxx_werror_flag=$ac_save_cxx_werror_flag
CXXFLAGS="$pgac_save_CXXFLAGS"
CXX="$pgac_save_CXX"
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CXX_cxxflags__Wcast_function_type" >&5
$as_echo "$pgac_cv_prog_CXX_cxxflags__Wcast_function_type" >&6; }
if test x"$pgac_cv_prog_CXX_cxxflags__Wcast_function_type" = x"yes"; then
CXXFLAGS="${CXXFLAGS} -Wcast-function-type"
fi
# This was included in -Wall/-Wformat in older GCC versions
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CC} supports -Wformat-security, for CFLAGS" >&5