Add shared library support (for macos, freebsd and several flavours o…

…f Linux)

Makefile.in

@@ -10,14 +10,19 @@ INCDIR=@prefix@/include
 PGMS=markdown
 SAMPLE_PGMS=mkd2html makepage
 @THEME@SAMPLE_PGMS+= theme
-MKDLIB=libmarkdown.a
+MKDLIB=libmarkdown.@LIBEXT@
 OBJS=mkdio.o markdown.o dumptree.o generate.o \
      resource.o docheader.o version.o toc.o css.o \
      xml.o Csio.o xmlpage.o basename.o emmatch.o \
      setup.o tags.o html5.o flags.o @AMALLOC@
 
 MAN3PAGES=mkd-callbacks.3 mkd-functions.3 markdown.3 mkd-line.3
 
+PIC_FLAGS=@PIC_FLAGS@
+SHARED_FLAGS=@SHARED_FLAGS@
+
+CFLAGS += ${PIC_FLAGS}
+
 all: $(PGMS) $(SAMPLE_PGMS)
 
 install: $(PGMS)
@@ -72,8 +77,9 @@ main.o: main.c mkdio.h config.h
 	$(CC) -I. -c main.c
 
 $(MKDLIB): $(OBJS)
-	$(AR) crv $(MKDLIB) $(OBJS)
-	$(RANLIB) $(MKDLIB)
+@MKSTATIC@	$(AR) crv $(MKDLIB) $(OBJS)
+@MKSTATIC@	$(RANLIB) $(MKDLIB)
+@MKSHARED@	$(CC) $(SHARED_FLAGS) $(PIC_FLAGS) -o $(MKDLIB) $(OBJS)
 
 verify: echo tools/checkbits.sh
 	@./echo -n "headers ... "; tools/checkbits.sh && echo "GOOD"

configure.inc

@@ -1120,6 +1120,58 @@ EOF
     rm -f /tmp/ngc$$ /tmp/ngc$$.c
 }
 
+#
+# AC_COMPILER_PIC checks for the compiler option to produce position independent
+# code.  At the moment we assume gcc semantics.
+#
+AC_COMPILER_PIC () {
+    AC_PROG_CC
+
+    LOGN "checking for C compiler option to produce PIC "
+    echo "int some_variable = 0;" > /tmp/ngc$$.c 
+
+    if $AC_CC -c -fPIC -o /tmp/ngc$$ /tmp/ngc$$.c $LIBS; then
+	AC_PIC_FLAGS="-fPIC"
+        LOG "($AC_PIC_FLAGS)"
+	__rc=0
+    else
+        LOG "(none)"
+	__rc=1
+    fi
+    rm -f /tmp/ngc$$ /tmp/ngc$$.c
+    return $__rc
+}
+
+#
+# AC_CC_SHLIBS checks if the C compiler can produce shared libraries
+# note that we compile and link a single object only in one step
+#
+AC_CC_SHLIBS () {
+    AC_PROG_CC
+    LOGN "checking whether the C compiler can build shared libraries "
+
+    echo "int some_variable = 0;" > /tmp/ngc$$.c 
+
+    if $AC_CC $AC_PICFLAG -shared -o /tmp/ngc$$.so /tmp/ngc$$.c; then
+	AC_SHLIB_FLAGS=-shared
+	AC_LIB_EXT=so
+        LOG "(yes; $AC_SHLIB_FLAGS)"
+	__rc=0
+    elif $AC_CC $AC_PICFLAG  -dynamiclib -o /tmp/ngc$$.so /tmp/ngc$$.c; then
+	# macosx
+	AC_SHLIB_FLAGS=' -dynamiclib'
+	AC_LIB_EXT=dylib
+        LOG "(yes; macos dylib)"
+	__rc=0
+    else
+        LOG "(no)"
+	__rc=1
+    fi
+
+    rm -f /tmp/ngc$$.so /tmp/ngc$$.c
+    return $__rc
+}
+
 
 #
 # AC_PROG_INSTALL finds the install program and guesses whether it's a 

configure.sh

@@ -10,7 +10,8 @@
 ac_help='--enable-amalloc	Enable memory allocation debugging
 --with-tabstops=N	Set tabstops to N characters (default is 4)
 --with-dl=X		Use Discount, Extra, or Both types of definition list
---enable-all-features	Turn on all stable optional features'
+--enable-all-features	Turn on all stable optional features
+--shared		Build shared libraries (default is static)'
 
 LOCAL_AC_OPTIONS='
 set=`locals $*`;
@@ -24,6 +25,9 @@ fi'
 locals() {
     K=`echo $1 | $AC_UPPERCASE`
     case "$K" in
+    --SHARED)
+                echo TRY_SHARED=T
+                ;;
     --ENABLE-ALL|--ENABLE-ALL-FEATURES)
 		echo WITH_AMALLOC=T
 		;;
@@ -48,6 +52,27 @@ BOTH)          AC_DEFINE 'USE_EXTRA_DL' 1
 esac
 
 AC_PROG_CC
+if test "$TRY_SHARED" && AC_COMPILER_PIC && AC_CC_SHLIBS; then
+    MAKE_SHARED=T
+    AC_SUB 'MKSHARED' ''
+    AC_SUB 'MKSTATIC' '#'
+
+    if [ "$AC_LIB_EXT" = "dylib" ]; then
+	# special horrible hack for macos shared library version.
+	eval `awk -F. '{ printf "COMPAT=%d.%d\n", $1, $2;
+			 printf "VERSION=%d.%d.%d\n", $1, $2, $3; }' VERSION`
+	AC_SHLIB_FLAGS="$AC_SHLIB_FLAGS -compatibility_version $COMPAT"
+	AC_SHLIB_FLAGS="$AC_SHLIB_FLAGS  -current_version $VERSION"
+    fi
+
+else
+    AC_SUB 'MKSHARED' '#'
+    AC_SUB 'MKSTATIC' ''
+fi
+
+AC_SUB 'PIC_FLAGS' "${MAKE_SHARED:+$AC_PIC_FLAGS}"
+AC_SUB 'SHARED_FLAGS' "${MAKE_SHARED:+$AC_SHLIB_FLAGS}"
+AC_SUB 'LIBEXT' "${AC_LIB_EXT:-a}"
 
 case "$AC_CC $AC_CFLAGS" in
 *-Wall*)    AC_DEFINE 'while(x)' 'while( (x) != 0 )'