New: build-id feature.

A build-id is a string optionally embedded into TXR at build
time which can be displayed with a command line option. It can
help developers who are juggling multiple builds in their
workspace to identify what they are running.

* Makefile (txr.o, txr-win.o): If a build_id has been
defined, then define the TXR_BUILD_ID macro on the command
line when compiling these object files.

* configure (build_id): New variable.
(help) Describe build_id.
(gen_config_make): Generate build_id and build_id_exp make
variables.

* txr.1: Documented --build-id option.

* tsr.c (build_id): Conditionally defined global variable.
(help): Brief help string for --build-id.
(txr_main): Process --build-id option.

4 files changed, 51 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index 6a67fe02..0a3d21af 100644
--- a/Makefile
+++ b/Makefile
@@ -329,6 +329,9 @@ opt/txr-win.o: TXR_CFLAGS += -DPROG_NAME=\"$(PROG)-win\" \
                              -DTXR_REL_PATH=\"$(bindir_rel)/$(PROG)-win$(EXE)\"
 dbg/txr-win.o: TXR_CFLAGS += -DPROG_NAME=\"$(PROG)-win-dbg\" \
                              -DTXR_REL_PATH=\"$(bindir_rel)/$(PROG)-win-dbg$(EXE)\"
+ifneq ($(build_id_exp),)
+$(call EACH_CONF,txr.o txr-win.o): TXR_CFLAGS += -DTXR_BUILD_ID=\"$(build_id_exp)\"
+endif
 $(call EACH_CONF,txr.o txr-win.o): TXR_CFLAGS += -DEXE_SUFF=\"$(EXE)\"
 $(call EACH_CONF,txr.o txr-win.o): TXR_CFLAGS += -DTXR_VER=\"$(txr_ver)\"
 
diff --git a/configure b/configure
index 3fa9b4eb..c5901d20 100755
--- a/configure
+++ b/configure
@@ -211,6 +211,7 @@ have_pkgconfig=
 libffi_cflags=
 darwin_target=
 android_target=
+build_id=
 
 #
 # Parse configuration variables
@@ -545,6 +546,22 @@ small-mem [$small_mem]
   and certain global book-keeping arrays in the generational garbage
   collector are smaller, resulting in more frequent collections.
 
+build-id [$build_id]
+
+  This option specifies the value of the build_id make variable.
+  The argument is GNU make syntax which calculates a string
+  that is inserted into the TXR executable. The string is reproduced
+  by reproduced using the txr --build-id. The default is that there
+  no build-id, and the --build-id option produces empty output.
+
+  If the argument value "git" is given, then the value is replaced
+  by syntax which which takes value of the output of the command
+  "git describe --tags --dirty",
+  executed in the source directory. This is recalculated each time
+  the txr.c source file is compiled.
+
+  The build_id variable can be overridden from the make command line.
+
 !
   exit 1
 fi
@@ -869,6 +886,19 @@ compiler_prefix := $compiler_prefix
 # prefix for non-compiler toolchain commands
 tool_prefix := $tool_prefix
 
+# build_id
+$(gitcmd='git describe --tags --dirty';
+  if [ "$build_id" = "git" ] ; then
+     if [ $build_in_srcdir ] ; then
+       printf 'build_id ?= $(shell %s)\n' "$gitcmd"
+     else
+       printf 'build_id ?= $(shell cd $(top_srcdir); %s)\n' "$gitcmd"
+     fi
+  else
+     printf 'build_id = %s\n' "$build_id"
+  fi)
+build_id_exp := \$(build_id)
+
 # do we compile in syslog support?
 have_syslog := $have_syslog
 
diff --git a/txr.1 b/txr.1
index 06c36736..d9e10f16 100644
--- a/txr.1
+++ b/txr.1
@@ -905,6 +905,12 @@ Use of \*(TX implies agreement with the liability disclaimer in the license.
 Prints a message on standard output which includes the program version,
 and then immediately causes \*(TX to terminate with a successful status.
 
+.coIP --build-id
+If \*(TX was built with an embedded build ID string, this
+option prints that string. Otherwise nothing is printed.
+In either case, \*(TX then immediately terminates with a successful
+status.
+
 .coIP --args
 The
 .code --args
diff --git a/txr.c b/txr.c
index fbb0f927..888fa4da 100644
--- a/txr.c
+++ b/txr.c
@@ -62,6 +62,9 @@
 #include "txr.h"
 
 const wchli_t *version = wli(TXR_VER);
+#ifdef TXR_BUILD_ID
+const wchli_t *build_id = wli(TXR_BUILD_ID);
+#endif
 wchar_t *progname;
 static const char *progname_u8;
 static val prog_path = nil, sysroot_path = nil;
@@ -139,6 +142,7 @@ static void help(void)
 "                       specified version of TXR.\n"
 "--help                 Reproduce this help text.\n"
 "--version              Display program version.\n"
+"--build-id             Print build ID string if compiled in.\n"
 "--license              Display software license.\n"
 "                       Use of txr implies agreement with the disclaimer\n"
 "                       section at the bottom of the license.\n"
@@ -700,6 +704,14 @@ int txr_main(int argc, char **argv)
         return 0;
       }
 
+      if (equal(opt, lit("build-id"))) {
+        drop_privilege();
+#ifdef TXR_BUILD_ID
+        format(std_output, lit("~a\n"), static_str(build_id), nao);
+#endif
+        return 0;
+      }
+
       if (equal(opt, lit("help"))) {
         drop_privilege();
         help();