Allow to build a static version of libosl.

This adds the new target libosl.a which creates an archive that can
be statically linked into applications. Currently this works only on
ELF-based systems including Linux, FreeBSD and NetBSD, but fails on
MacOS. So it is not built automatically.

Unfortunately, creating libosl.a turned out to be trickier than
expected, because -fvisibility=hidden works only for dynamic libraries.
So we need a different method to hide non-static internal symbols
like make_message() which must not be global (external) because they
might clash with symbols used in the application.

objcopy(1) does the trick but we must provide a list of exceptional
symbols that should not be made local. This list is generated from
the osl.h header file.

diff --git a/Makefile b/Makefile
index 100a486b06bf6fb83ac8de3bf743268ea93c3dd8..967b00d205939370430b99cfd9f89c0de7207a13 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -18,6 +18,8 @@ endif
 MKDIR := mkdir -p
 RM := rm -f
 LN := ln
+LD := ld
+OBJCOPY := objcopy
 
 # libosl's versioning consists of three numbers. Let's call them x, y and z.
 # The way x, y and z are interpreted depends on the OS.
@@ -144,6 +146,13 @@ oslfsck.1: oslfsck
 $(realname): $(objects)
        $(CC) $(LDFLAGS) -o $@ $(objects)
 
+$(libname).sym: osl.h.in
+       sed -Ene '/^int|^const/{s/.*(osl_.*)\(.*/\1/; p;}' $< > $@
+$(libname).ga: $(objects)
+       $(LD) -r -o $@ $(objects)
+lib$(libname).a: $(libname).ga $(libname).sym
+       $(OBJCOPY) --keep-global-symbols $(libname).sym $(libname).ga $@
+
 osl_errors.h: errlist
        echo '/** public error codes of the osl library. */' > $@
        sed -e 's/\([A-Z_]*\)   .*/     E_OSL_\1/' \
@@ -162,7 +171,7 @@ osl.h: osl.h.in osl_errors.h Makefile
        echo '#endif /* _OSL_H */' >> $@
 clean:
        rm -f *.o $(realname) osl.h osl_errors.h errtab.h fsck.cmdline.h \
-               fsck.cmdline.c oslfsck
+               fsck.cmdline.c oslfsck *.a *.ga *.sym
 
 distclean: clean
        rm -f web/index.html web/oslfsck.1.html web/osl.png