Apisupport

.gitignore

@@ -1,5 +1,6 @@
 # These also apply to all subdirectories.
 *.o
+apisupport-config.h
 cpusupport-config.h
 posix-flags.sh
 # Test binaries and compiled files.

Makefile

@@ -22,20 +22,22 @@ TEST_CMD=	tests/test_libcperciva.sh
 
 ### Shared code between Tarsnap projects.
 
-all:	cpusupport-config.h posix-flags.sh
+all:	apisupport-config.h cpusupport-config.h posix-flags.sh
 	export CFLAGS="$${CFLAGS:-${CFLAGS_DEFAULT}}";	\
 	. ./posix-flags.sh;				\
 	. ./cpusupport-config.h;			\
+	. ./apisupport-config.h;			\
 	export HAVE_BUILD_FLAGS=1;			\
 	for D in ${PROGS} ${TESTS}; do			\
 		( cd $${D} && ${MAKE} all ) || exit 2;	\
 	done
 
 # For "loop-back" building of a subdirectory
-buildsubdir: cpusupport-config.h posix-flags.sh
-	. ./cpusupport-config.h; \
-	. ./posix-flags.sh; \
-	export HAVE_BUILD_FLAGS=1; \
+buildsubdir: apisupport-config.h cpusupport-config.h posix-flags.sh
+	. ./posix-flags.sh;				\
+	. ./cpusupport-config.h;			\
+	. ./apisupport-config.h;			\
+	export HAVE_BUILD_FLAGS=1;			\
 	cd ${BUILD_SUBDIR} && ${MAKE} ${BUILD_TARGET}
 
 posix-flags.sh:
@@ -52,6 +54,16 @@ posix-flags.sh:
 		:;							\
 	fi > $@
 
+apisupport-config.h:
+	if [ -d ${LIBCPERCIVA_DIR}/apisupport/ ]; then			\
+		export CC="${CC}";					\
+		command -p sh						\
+		    ${LIBCPERCIVA_DIR}/apisupport/Build/apisupport.sh	\
+		    "$$PATH";						\
+	else								\
+		:;							\
+	fi > $@
+
 cpusupport-config.h:
 	if [ -d ${LIBCPERCIVA_DIR}/cpusupport/ ]; then			\
 		export CC="${CC}";					\
@@ -69,7 +81,7 @@ install:	all
 	done
 
 clean:
-	rm -f cpusupport-config.h posix-flags.sh
+	rm -f apisupport-config.h cpusupport-config.h posix-flags.sh
 	for D in ${PROGS} ${TESTS}; do				\
 		( cd $${D} && ${MAKE} clean ) || exit 2;	\
 	done

Makefile.BSD

@@ -14,15 +14,15 @@ TESTS=	tests/buildall							\
 	tests/setuidgid							\
 	tests/sha256							\
 	tests/valgrind
-PUBLISH= ${PROGS} COPYRIGHT STYLE POSIX alg cpusupport crypto datastruct \
-	events network tests util
+PUBLISH= ${PROGS} COPYRIGHT STYLE POSIX alg apisupport cpusupport	\
+	 datastruct events network tests util
 
 ### Shared code between Tarsnap projects.
 
 # These definitions improve the readability of the below material.
 MAKEBSD:=	${MAKE} -f Makefile.BSD
 RELEASEDATE!=	date "+%B %d, %Y"
-CFLAGS_HARDCODED=	-D_POSIX_C_SOURCE=200809L -D_XOPEN_SOURCE=700 -DCPUSUPPORT_CONFIG_FILE=\\\"cpusupport-config.h\\\"
+CFLAGS_HARDCODED=	-D_POSIX_C_SOURCE=200809L -D_XOPEN_SOURCE=700 -DCPUSUPPORT_CONFIG_FILE=\\\"cpusupport-config.h\\\" -DAPISUPPORT_CONFIG_FILE=\\\"apisupport-config.h\\\"
 
 # This creates (and deletes) a fake cpusupport-config.h that is
 # blank (and thus does not require any special CFLAGS to compile).
@@ -32,7 +32,7 @@ ${D}/Makefile::
 	echo '# AUTOGENERATED FILE, DO NOT EDIT' >> $@
 	( cd ${D} && printf 'PROG=' && ${MAKEBSD} -V PROG ) >> $@
 	( cd ${D} && printf 'MAN1=' && ${MAKEBSD} -V MAN1 ) >> $@
-	( cd ${D} && printf 'SRCS=' && ${MAKEBSD} -V SRCS | sed -e 's| cpusupport-config.h||' ) >> $@
+	( cd ${D} && printf 'SRCS=' && ${MAKEBSD} -V SRCS | sed -e 's| cpusupport-config.h||' | sed -e 's| apisupport-config.h||' ) >> $@
 	( cd ${D} && printf 'IDIRS=' && ${MAKEBSD} -V IDIRS ) >> $@
 	( cd ${D} && printf 'LDADD_REQ=' && ${MAKEBSD} -V LDADD_REQ ) >> $@
 	( cd ${D} && printf 'SUBDIR_DEPTH=' && ${MAKEBSD} -V SUBDIR_DEPTH ) >> $@
@@ -43,18 +43,19 @@ ${D}/Makefile::
 	else							\
 		cat Makefile.prog >> $@	;			\
 	fi
-	rm -f cpusupport-config.h
-	touch cpusupport-config.h
+	rm -f apisupport-config.h cpusupport-config.h
+	touch apisupport-config.h cpusupport-config.h
 	( cd ${D} && ${MAKEBSD} -V SRCS |	\
 	    sed -e 's| cpusupport-config.h||' |	\
+	    sed -e 's| apisupport-config.h||' |	\
 	    tr ' ' '\n' |		\
 	    sed -E 's/.c$$/.o/' |	\
 	    while read F; do		\
 		S=`${MAKEBSD} source-$${F}`;	\
 		CF=`${MAKEBSD} cflags-$${F}`;	\
 		IDIRS=`${MAKEBSD} -V IDIRS`;	\
 		SUBDIR_DEPTH=`${MAKEBSD} -V SUBDIR_DEPTH`;	\
-		echo `${CPP} $${S} -std=c99 -DCPUSUPPORT_CONFIG_FILE=\"cpusupport-config.h\" -I$${SUBDIR_DEPTH} $${IDIRS} -MM -MT $${F}` \
+		echo `${CPP} $${S} -std=c99 -DCPUSUPPORT_CONFIG_FILE=\"cpusupport-config.h\" -DAPISUPPORT_CONFIG_FILE=\"apisupport-config.h\" -I$${SUBDIR_DEPTH} $${IDIRS} -MM -MT $${F}` \
 			| sed -e 's| \\ | |g'; \
 		echo "	\$${CC} \$${CFLAGS_POSIX} ${CFLAGS_HARDCODED} $${CF} -I$${SUBDIR_DEPTH} \$${IDIRS} \$${CPPFLAGS} \$${CFLAGS} -c $${S} -o $${F}"; \
 	    done ) >> $@
@@ -81,7 +82,7 @@ ${D}/Makefile::
 		    Makefile > Makefile.new );				\
 		( cd ${D} && mv Makefile.new Makefile );		\
 	fi
-	rm -f cpusupport-config.h
+	rm -f apisupport-config.h cpusupport-config.h
 .endfor
 
 Makefiles:

apisupport/Build/apisupport.sh

@@ -0,0 +1,44 @@
+# Should be sourced by `command -p sh path/to/apisupport.sh "$PATH"` from
+# within a Makefile.
+if ! [ ${PATH} = "$1" ]; then
+	echo "WARNING: POSIX violation: $SHELL's command -p resets \$PATH" 1>&2
+	PATH=$1
+fi
+# Standard output should be written to apisupport-config.h, which is both a
+# C header file defining APISUPPORT_ARCH_FEATURE macros and sourceable sh
+# code which sets CFLAGS_ARCH_FEATURE environment variables.
+SRCDIR=`command -p dirname "$0"`
+
+feature() {
+	ARCH=$1
+	FEATURE=$2
+	shift 2;
+	if ! [ -f ${SRCDIR}/apisupport-$ARCH-$FEATURE.c ]; then
+		return
+	fi
+	printf "Checking if compiler supports $ARCH $FEATURE feature..." 1>&2
+	for CFLAG in "$@"; do
+		if ${CC} ${CFLAGS} -D_POSIX_C_SOURCE=200809L ${CFLAG}	\
+		    ${SRCDIR}/apisupport-$ARCH-$FEATURE.c 2>/dev/null; then
+			rm -f a.out
+			break;
+		fi
+		CFLAG=NOTSUPPORTED;
+	done
+	case $CFLAG in
+	NOTSUPPORTED)
+		echo " no" 1>&2
+		;;
+	"")
+		echo " yes" 1>&2
+		echo "#define APISUPPORT_${ARCH}_${FEATURE} 1"
+		;;
+	*)
+		echo " yes, via $CFLAG" 1>&2
+		echo "#define APISUPPORT_${ARCH}_${FEATURE} 1"
+		echo "#ifdef apisupport_dummy"
+		echo "export CFLAGS_${ARCH}_${FEATURE}=\"${CFLAG}\""
+		echo "#endif"
+		;;
+	esac
+}

apisupport/apisupport.h

@@ -0,0 +1,106 @@
+#ifndef _APISUPPORT_H_
+#define _APISUPPORT_H_
+
+/*
+ * To enable support for non-portable API features at compile time, one or
+ * more APISUPPORT_ARCH_FEATURE macros should be defined.  This can be done
+ * directly on the compiler command line via -D APISUPPORT_ARCH_FEATURE or
+ * -D APISUPPORT_ARCH_FEATURE=1; or a file can be created with the
+ * necessary #define lines and then -D APISUPPORT_CONFIG_FILE=apiconfig.h
+ * (or similar) can be provided to include that file here.
+ */
+#ifdef APISUPPORT_CONFIG_FILE
+#include APISUPPORT_CONFIG_FILE
+#endif
+
+/**
+ * The APISUPPORT_FEATURE macro declares the necessary variables and
+ * functions for detecting API feature support at run time.  The function
+ * defined in the macro acts to cache the result of the ..._detect function
+ * using the ..._present and ..._init variables.  The _detect function and the
+ * _present and _init variables are turn defined by APISUPPORT_FEATURE_DECL in
+ * appropriate apisupport_foo_bar.c file.
+ *
+ * In order to allow APISUPPORT_FEATURE to be used for features which do not
+ * have corresponding APISUPPORT_FEATURE_DECL blocks in another source file,
+ * we abuse the C preprocessor: If APISUPPORT_${enabler} is defined to 1, then
+ * we access _present_1, _init_1, and _detect_1; but if it is not defined, we
+ * access _present_APISUPPORT_${enabler} etc., which we define as static, thus
+ * preventing the compiler from emitting a reference to an external symbol.
+ *
+ * In this way, it becomes possible to issue APISUPPORT_FEATURE invocations
+ * for nonexistent features without running afoul of the requirement that
+ * "If an identifier declared with external linkage is used... in the entire
+ * program there shall be exactly one external definition" (C99 standard, 6.9
+ * paragraph 5).  In practice, this means that users of the apisupport code
+ * can omit build and runtime detection files without changing the framework
+ * code.
+ */
+#define APISUPPORT_FEATURE__(arch_feature, enabler, enabled)					\
+	static int apisupport_ ## arch_feature ## _present ## _APISUPPORT_ ## enabler;		\
+	static int apisupport_ ## arch_feature ## _init ## _APISUPPORT_ ## enabler;		\
+	static inline int apisupport_ ## arch_feature ## _detect ## _APISUPPORT_ ## enabler(void) { return (0); }	\
+	extern int apisupport_ ## arch_feature ## _present_ ## enabled;				\
+	extern int apisupport_ ## arch_feature ## _init_ ## enabled;				\
+	int apisupport_ ## arch_feature ## _detect_ ## enabled(void);				\
+												\
+	static inline int									\
+	apisupport_ ## arch_feature(void)							\
+	{											\
+												\
+		if (apisupport_ ## arch_feature ## _present_ ## enabled)			\
+			return (1);								\
+		else if (apisupport_ ## arch_feature ## _init_ ## enabled)			\
+			return (0);								\
+		apisupport_ ## arch_feature ## _present_ ## enabled = 				\
+		    apisupport_ ## arch_feature ## _detect_ ## enabled();			\
+		apisupport_ ## arch_feature ## _init_ ## enabled = 1;				\
+		return (apisupport_ ## arch_feature ## _present_ ## enabled); 			\
+	}											\
+	static void (* apisupport_ ## arch_feature ## _dummyptr)(void);				\
+	static inline void									\
+	apisupport_ ## arch_feature ## _dummyfunc(void)						\
+	{											\
+												\
+		(void)apisupport_ ## arch_feature ## _present ## _APISUPPORT_ ## enabler;	\
+		(void)apisupport_ ## arch_feature ## _init ## _APISUPPORT_ ## enabler;		\
+		(void)apisupport_ ## arch_feature ## _detect ## _APISUPPORT_ ## enabler;	\
+		(void)apisupport_ ## arch_feature ## _present_ ## enabled;			\
+		(void)apisupport_ ## arch_feature ## _init_ ## enabled;				\
+		(void)apisupport_ ## arch_feature ## _detect_ ## enabled;			\
+		(void)apisupport_ ## arch_feature ## _dummyptr;					\
+	}											\
+	static void (* apisupport_ ## arch_feature ## _dummyptr)(void) = apisupport_ ## arch_feature ## _dummyfunc;	\
+	struct apisupport_ ## arch_feature ## _dummy
+#define APISUPPORT_FEATURE_(arch_feature, enabler, enabled)	\
+	APISUPPORT_FEATURE__(arch_feature, enabler, enabled)
+#define APISUPPORT_FEATURE(arch, feature, enabler)				\
+	APISUPPORT_FEATURE_(arch ## _ ## feature, enabler, APISUPPORT_ ## enabler)
+
+/*
+ * APISUPPORT_FEATURE_DECL(arch, feature):
+ * Macro which defines variables and provides a function declaration for
+ * detecting the presence of "feature" on the "arch" architecture.  The
+ * function body following this macro expansion must return nonzero if the
+ * feature is present, or zero if the feature is not present or the detection
+ * fails for any reason.
+ */
+#define APISUPPORT_FEATURE_DECL(arch, feature)				\
+	extern int apisupport_ ## arch ## _ ## feature ## _present_1;	\
+	extern int apisupport_ ## arch ## _ ## feature ## _init_1;	\
+	int apisupport_ ## arch ## _ ## feature ## _present_1 = 0;	\
+	int apisupport_ ## arch ## _ ## feature ## _init_1 = 0;		\
+	int apisupport_ ## arch ## _ ## feature ## _detect_1(void); \
+	int								\
+	apisupport_ ## arch ## _ ## feature ## _detect_1(void)
+
+/*
+ * List of features.  If a feature here is not enabled by the appropriate
+ * APISUPPORT_ARCH_FEATURE macro being defined, it has no effect; but if the
+ * relevant macro may be defined (e.g., by Build/apisupport.sh successfully
+ * compiling Build/apisupport-ARCH-FEATURE.c) then the C file containing the
+ * corresponding run-time detection code (apisupport_arch_feature.c) must be
+ * compiled and linked in.
+ */
+
+#endif /* !_APISUPPORT_H_ */