From eaa8695b76849d8156826a8919a591555c81a3dd Mon Sep 17 00:00:00 2001
From: Ron Yorston <rmy@pobox.com>
Date: Wed, 22 May 2024 08:58:13 +0100
Subject: make: add support for CURDIR macro

Austin Group defect report 1626 introduced support for the CURDIR
macro:

   https://www.austingroupbugs.net/view.php?id=1626

Implement this as a POSIX 202X feature.

Adds 160-176 bytes.
---
 miscutils/make.c     | 33 ++++++++++++++++++++++++++++-----
 testsuite/make.tests | 25 +++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/miscutils/make.c b/miscutils/make.c
index fca00d8e3..f594e196b 100644
--- a/miscutils/make.c
+++ b/miscutils/make.c
@@ -2681,9 +2681,10 @@ expand_makeflags(void)
 }
 
 // These macros require special treatment
-#define MAKEFLAGS_SHELL "MAKEFLAGS\0SHELL\0"
+#define SPECIAL_MACROS "MAKEFLAGS\0SHELL\0CURDIR\0"
 #define MAKEFLAGS 0
 #define SHELL 1
+#define CURDIR 2
 
 /*
  * Instantiate all macros in an argv-style array of pointers.  Stop
@@ -2697,7 +2698,7 @@ process_macros(char **argv, int level)
 	char *p;
 
 	for (; *argv; argv++) {
-		int immediate = 0;
+		int idx, immediate = 0;
 
 		if (!(p = strchr(*argv, '='))) {
 			// Skip targets on the command line
@@ -2714,8 +2715,15 @@ process_macros(char **argv, int level)
 			immediate = M_IMMEDIATE;
 			p[-2] = '\0';
 		} else
-		*p = '\0';
-		if (level != 3 || index_in_strings(MAKEFLAGS_SHELL, *argv) < 0) {
+			*p = '\0';
+
+		/* We want to process _most_ macro assignments.
+		 * There are exceptions for particular values from the
+		 * environment (level 3). */
+		idx = index_in_strings(SPECIAL_MACROS, *argv);
+		if (!(level == 3 &&
+				(idx == MAKEFLAGS || idx == SHELL ||
+					(idx == CURDIR && !useenv && !POSIX_2017)))) {
 			if (immediate) {
 				char *exp = expand_macros(p + 1, FALSE);
 				setmacro(*argv, exp, level | immediate);
@@ -2724,6 +2732,7 @@ process_macros(char **argv, int level)
 				setmacro(*argv, p + 1, level);
 			}
 		}
+
 		*p = '=';
 		if (immediate)
 			p[-2] = ':';
@@ -2766,7 +2775,7 @@ update_makeflags(void)
 	for (i = 0; i < HTABSIZE; ++i) {
 		for (mp = macrohead[i]; mp; mp = mp->m_next) {
 			if (mp->m_level == 1 || mp->m_level == 2) {
-				int idx = index_in_strings(MAKEFLAGS_SHELL, mp->m_name);
+				int idx = index_in_strings(SPECIAL_MACROS, mp->m_name);
 				if (idx == MAKEFLAGS)
 					continue;
 				macro = xzalloc(strlen(mp->m_name) + 2 * strlen(mp->m_val) + 1);
@@ -2960,6 +2969,20 @@ int make_main(int argc UNUSED_PARAM, char **argv)
 
 	setmacro("SHELL", DEFAULT_SHELL, 4);
 	setmacro("MAKE", path, 4);
+	if (!POSIX_2017) {
+		char *cwd = xrealloc_getcwd_or_warn(NULL);
+
+		if (cwd) {
+			if (!useenv) {
+				// Export cwd to environment, if necessary
+				char *envcwd = getenv("CURDIR");
+				if (envcwd && strcmp(cwd, envcwd) != 0)
+					setenv("CURDIR", cwd, 1);
+			}
+			setmacro("CURDIR", cwd, 4);
+		}
+		free(cwd);
+	}
 	free((void *)newpath);
 
 	if (!makefiles) {	// Look for a default Makefile
diff --git a/testsuite/make.tests b/testsuite/make.tests
index 546dca7d5..fdbb4ccfc 100755
--- a/testsuite/make.tests
+++ b/testsuite/make.tests
@@ -377,6 +377,31 @@ target:
 b}
 '
 
+# The CURDIR macro is supported in POSIX 202X.
+testing "make CURDIR macro" \
+	"make -f -" \
+	"OK\n" "" '
+target:
+	@test "$(CURDIR)" = "$$(pwd)" && echo OK
+'
+# The CURDIR environment variable doesn't affect the macro
+export CURDIR=/you/are/here
+testing "make CURDIR macro not affected by environment" \
+	"make -f -" \
+	"OK\n" "" '
+target:
+	@test "$(CURDIR)" != "/you/are/here" && echo OK
+'
+
+# The -e option makes the CURDIR macro match the environment
+testing "make with -e CURDIR macro is affected by the environment" \
+	"make -e -f -" \
+	"/you/are/here\n" "" '
+target:
+	@echo $(CURDIR)
+'
+unset CURDIR
+
 # POSIX 202X permits additional characters in macro and target names
 testing "make allow - and / in target names, - in macro names" \
 	"make -f -" \
-- 
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