Re: -Werror=implicit-function-declaration by default?

["Johnson, Andrew N. via Core-talk" <core-talk at aps.anl.gov>]

On Dec 18, 2020, at 11:41 AM, Michael Davidsaver via Core-talk <core-talk at aps.anl.gov> wrote:

I'd like to start treating calls to undeclared functions in C as errors,
at least in CI builds.  This has long been an error in c++, but is only
a warning with C.

No major objections from here.

I can easily add this only for the CI jobs w/ GCC with:

cat <<EOF >> configure/CONFIG_SITE.local
USR_CFLAGS += -Werror-implicit-function-declaration
EOF

Note: the newer -Werror=* syntax was added with GCC 4.2.  As of 8.3
the older flag is still recognized (thank you GCC).

VxWorks 6.8 (gcc 4.1.3) doesn’t list -Werror= as supported but does show Werror-implicit-function-declaration as you say.

My question is whether this should become a default for all builds?

(in WARN_CFLAGS_YES?)

For gcc builds I think yes (so in configure/CONFIG.gnuCommon).

My inclination is yes.  I've certainly never intended to rely on an implicit
declaration, but have occasionally done so unwittingly as a result of
a missing #include.

Ditto, nowadays we shouldn’t have any code using implicits (of any sort).

- Andrew

-- 

Complexity comes for free, simplicity you have to work for.