I have a perplexing problem in compiling source files:

make[1]: Leaving directory '/home/stevet/stuff/src/projects/olock-beta/arch'
ar cr libolock.a anon_pages.o aobm.o apool.o asm_ops.o bool.o debugging.o
microsecond_time.o nanosecond_time.o obm.o olock.o os_linux.o platform.o
posix_mmap.o posix_threads.o statistics.o
ranlib libolock.a
make -C test
make[1]: Entering directory
'/home/stevet/stuff/src/projects/olock-beta/test'
gcc10.4  -D _DEFAULT_SOURCE -DARCH_64 -DOLOCK_192 -DLINUX -I./ -I../
-pthread -m64 -std=c99 -Wall -Wextra -Werror -fdiagnostics-color=never -O
-ggdb  -DUSE_OBM -o otest otest.c ../libolock.a
/usr/bin/ld: ../libolock.a(debugging.o): in function `apool_init_freelist':
/home/stevet/stuff/src/projects/olock-beta/./apool.h:92: multiple
definition of `apool_init_freelist';
/tmp/ccZflz99.o:/home/stevet/stuff/src/projects/olock-beta/test/../apool.h:92:
first defined here
/usr/bin/ld: ../libolock.a(olock.o): in function `apool_init_freelist':
/home/stevet/stuff/src/projects/olock-beta/./apool.h:92: multiple
definition of `apool_init_freelist';
/tmp/ccZflz99.o:/home/stevet/stuff/src/projects/olock-beta/test/../apool.h:92:
first defined here
/usr/bin/ld: ../libolock.a(platform.o): in function `apool_init_freelist':
/home/stevet/stuff/src/projects/olock-beta/./apool.h:92: multiple
definition of `apool_init_freelist';
/tmp/ccZflz99.o:/home/stevet/stuff/src/projects/olock-beta/test/../apool.h:92:
first defined here
/usr/bin/ld: ../libolock.a(posix_threads.o): in function
`apool_init_freelist':
/home/stevet/stuff/src/projects/olock-beta/./apool.h:92: multiple
definition of `apool_init_freelist';
/tmp/ccZflz99.o:/home/stevet/stuff/src/projects/olock-beta/test/../apool.h:92:
first defined here
/usr/bin/ld: ../libolock.a(anon_pages.o): in function `apool_init_freelist':
/home/stevet/stuff/src/projects/olock-beta/./apool.h:92: multiple
definition of `apool_init_freelist';
/tmp/ccZflz99.o:/home/stevet/stuff/src/projects/olock-beta/test/../apool.h:92:
first defined here
/usr/bin/ld: ../libolock.a(os_linux.o): in function `apool_init_freelist':
/home/stevet/stuff/src/projects/olock-beta/./apool.h:92: multiple
definition of `apool_init_freelist';
/tmp/ccZflz99.o:/home/stevet/stuff/src/projects/olock-beta/test/../apool.h:92:
first defined here
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:31: otest] Error 1
make[1]: Leaving directory '/home/stevet/stuff/src/projects/olock-beta/test'
make: *** [Makefile:36: test] Error 2

Actually there are two problems, and I had to do something stupid to get
this error, so that one first.

All of the .h files are referenced in a particular sequence in platform.h
and each source module compiled above only includes the consolidated header.

In microsecond_time.h  there are several definitions, one of which is
"typedef s64 T64;".  Now the T64 type is used all over the place and is
defined correctly _except_ for microsecond_time.h.   When
microsecond_time.c is compiled the typedef is missing from the --save-temps
file, whereas it is present in all of the other compilation units.  To
fudge it I modified microsecond_time.c to include only the necessary
headers and added a redundant "typedef s64 T64" line in microsecond_time.c
-- and it compiles!

The second problem is shaped as follows:  apool_init_freelist() is defined
in apool.h as __inline__ and is referenced by two more __inline__ macros,
like this:

__inline__ void apool_init_freelist(apool * a) {
   a->free_list = 1;
   apool_fl_nr_cells(a, 1) = a->pool.nr_cells - 1;  // macro
   apool_fl_next(a, 1) = 0;                                    // macro
   a->nr_free = a->pool.nr_cells - 1;
}

...
__inline__ void init_apool_struct(apool * p)
{
   p->nr_free = p->pool.nr_cells - 1;
   p->pool.offset = sizeof(apool);
   apool_init_freelist(p);
}

These functions aren't used anywhere yet so no code whatsoever should be
generated for apool_init_freelist().   And yet, as you can see in the
linker errors, several modules that do not reference those functions at all
have a symbol and code for the "inline" function.

In comp.lang.c (and in 2018) there is a thread that discusses an eerily
similar problem but in that case it seems to be triggered by a "#define
__attribute__(x)" before inclusion of normal libc headers (affecting atoi)
:   (damn google)

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiP--P5qpT-AhVjADQIHSMZBmQQFnoECAkQAQ&url=https%3A%2F%2Fgroups.google.com%2Fg%2Fcomp.lang.c%2Fc%2F0fqzRqf--ds&usg=AOvVaw3gu9TODPn58URUag7Y6B5d

The followups do not reveal a cause; the original poster found a workaround
that doesn't apply to my situation.  I could in theory work around this
problem by changing all the __inline__ (in .h files) functions to macros,
or by moving all the inline functions to the .c files, but the whole point
of the "apool" abstraction is that it is a very thin layer and should be
inline.   If I change all the header inline functions to macros it begs the
reason for having __inline__ at all.

At any rate both of these problems are entirely mysterious to me.  I can't
see a reason gcc would produce static copies of a function that is never
used in some but not all source modules where it is defined.  And second, I
should be getting an error for a redefined typedef as things stand with
microsecond time.c.

One last thing, if I compile with -O0 a whole slew of functions declared
"inline" are silently deleted and show up as missing symbols in the static
library link.

I am at a loss.  Suggestions for what to look for would be appreciated.