add infrastructure to record and report the version of libc.so

this is still experimental and subject to change. for git checkouts,
an attempt is made to record the exact revision to aid in bug reports
and debugging. no version information is recorded in the static libc.a
or binaries it's linked into.

Makefile

@@ -20,6 +20,7 @@ SRCS = $(sort $(wildcard src/*/*.c arch/$(ARCH)/src/*.c))
 OBJS = $(SRCS:.c=.o)
 LOBJS = $(OBJS:.o=.lo)
 GENH = include/bits/alltypes.h
+GENH_INT = src/internal/version.h
 IMPH = src/internal/stdio_impl.h src/internal/pthread_impl.h src/internal/libc.h
 
 LDFLAGS = 
@@ -64,7 +65,7 @@ clean:
 	rm -f $(LOBJS)
 	rm -f $(ALL_LIBS) lib/*.[ao] lib/*.so
 	rm -f $(ALL_TOOLS)
-	rm -f $(GENH) 
+	rm -f $(GENH) $(GENH_INT)
 	rm -f include/bits
 
 distclean: clean
@@ -79,6 +80,11 @@ include/bits/alltypes.h.in: include/bits
 include/bits/alltypes.h: include/bits/alltypes.h.in include/alltypes.h.in tools/mkalltypes.sed
 	sed -f tools/mkalltypes.sed include/bits/alltypes.h.in include/alltypes.h.in > $@
 
+src/internal/version.h: $(wildcard VERSION .git .git/*)
+	printf '#define VERSION "%s"\n' "$$(sh tools/version.sh)" > $@
+
+src/internal/version.lo: src/internal/version.h
+
 src/ldso/dynlink.lo: arch/$(ARCH)/reloc.h
 
 crt/crt1.o crt/Scrt1.o: $(wildcard arch/$(ARCH)/crt_arch.h)

VERSION

@@ -0,0 +1 @@
+0.9.14

src/internal/version.c

@@ -0,0 +1,12 @@
+#ifdef SHARED
+
+#include "version.h"
+
+static const char version[] = VERSION;
+
+const char *__libc_get_version()
+{
+	return version;
+}
+
+#endif

src/ldso/dynlink.c

@@ -93,6 +93,8 @@ void __init_ssp(size_t *);
 void *__install_initial_tls(void *);
 void __init_libc(char **, char *);
 
+const char *__libc_get_version(void);
+
 static struct dso *head, *tail, *ldso, *fini_head;
 static char *env_path, *sys_path;
 static unsigned long long gencnt;
@@ -1040,8 +1042,11 @@ void *__dynlink(int argc, char **argv)
 		*argv++ = (void *)-1;
 		if (argv[0] && !strcmp(argv[0], "--")) *argv++ = (void *)-1;
 		if (!argv[0]) {
-			dprintf(2, "musl libc/dynamic program loader\n");
-			dprintf(2, "usage: %s pathname%s\n", ldname,
+			dprintf(2, "musl libc\n"
+				"Version %s\n"
+				"Dynamic Program Loader\n"
+				"Usage: %s [--] pathname%s\n",
+				__libc_get_version(), ldname,
 				ldd_mode ? "" : " [args]");
 			_exit(1);
 		}

tools/version.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+if test -d .git ; then
+if type git >/dev/null 2>&1 ; then
+git describe --tags --match 'v[0-9]*' 2>/dev/null \
+| sed -e 's/^v//' -e 's/-/-git-/'
+else
+sed 's/$/-git/' < VERSION
+fi
+else
+cat VERSION
+fi