The internal header redefines the some internal argp functions with
attribute_hidden, which triggers clang warning of mismatched attributes.

Reviewed-by: Collin Funk <collin.funk1@gmail.com>

The argp code uses macro redefinitions to avoid duplicating static inline
implementations for argp_usage, _option_is_short, and _option_is_end.
However, this causes build issues with clang, as some function prototypes
are redefined to add the hidden attribute with libc_hidden_proto.

To avoid extensive changes to internal headers, just expand the function
implementations and avoid the macro redefine tricks.

Reviewed-by: Collin Funk <collin.funk1@gmail.com>

From gnulib commits 06094e390b0 and 88033d3779362a.
Reviewed-by: Florian Weimer <fweimer@redhat.com>

Fix variables in Makefiles:

1. There is a tab, not a space, between "variable" and =, +=, :=.
2. The last entry doesn't have a trailing \.

and sort them.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>

Replace 0 by NULL and {0} by {}.

Omit a few cases that aren't so trivial to fix.

Link: <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117059>
Link: <https://software.codidact.com/posts/292718/292759#answer-292759>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

Even though the alloca usage is relatively small and fixed size the code
can be written without using alloca.  Convert to local variables.

Checked on x86_64-linux-gnu.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

When enabling _FORTIFY_SOURCE, some functions now lead to warnings when
their result is not checked.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>