Redundant declarations in header file breaking build

[FinnG]

Hi there, I'm trying to build libpicrin.a for use in an embedded project. I'm using -Werror -Wredundant-decls and unfortunately this means that the combination of picrin.h and picrin/value.h don't build.

Here is the diff required to reproduce in libpicrin's source:

diff --git a/Makefile b/Makefile
index 9634630..c562a82 100644
--- a/Makefile
+++ b/Makefile
@@ -36,7 +36,7 @@ LIBPICRIN_HEADERS = \
 	object.h\
 	state.h
 
-CFLAGS += -I./include -Wall -Wextra -g
+CFLAGS += -I./include -Wall -Wextra -g -Werror -Wredundant-decls
 
 mini-picrin: ext/main.o libpicrin.a
 	$(CC) $(CFLAGS) -o $@ ext/main.o libpicrin.a

and the compiler output:

gcc -I./include -Wall -Wextra -g -Werror -Wredundant-decls   -c -o ext/main.o ext/main.c
In file included from ext/main.c:5:0:
./include/picrin.h:86:6: error: redundant redeclaration of 'pic_eq_p' [-Werror=redundant-decls]
 bool pic_eq_p(pic_state *, pic_value, pic_value);
      ^
In file included from ./include/picrin.h:54:0,
                 from ext/main.c:5:
./include/picrin/value.h:250:1: note: previous definition of 'pic_eq_p' was here
 pic_eq_p(pic_state *PIC_UNUSED(pic), pic_value x, pic_value y)
 ^
In file included from ext/main.c:5:0:
./include/picrin.h:87:6: error: redundant redeclaration of 'pic_eqv_p' [-Werror=redundant-decls]
 bool pic_eqv_p(pic_state *, pic_value, pic_value);
      ^
In file included from ./include/picrin.h:54:0,
                 from ext/main.c:5:
./include/picrin/value.h:256:1: note: previous definition of 'pic_eqv_p' was here
 pic_eqv_p(pic_state *PIC_UNUSED(pic), pic_value x, pic_value y)
 ^
... and so on

Compiler version, just in case it's relevant.

gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Note that although I'm using the build of libpicrin.a as an example here, this is a problem in the header files, so it happens when I #include <include/picrin.h> into my own project.

From looking through things here, I think the problem is because the static inline function definitions in include/picrin/value.h are declared after they're included in include/picrin.h. One solution would be to move these functions into a C file (perhaps a new value.c file?), so they're not shared between compilation units but I guess they're static inline for performance reasons so that might not be desirable?

If you have a solution in mind, I'd be happy to submit a pull request.