From 04e7f6dd0fc57ab98f39fb6fc9df610d0737ff17 Mon Sep 17 00:00:00 2001
From: Ron Yorston <rmy@pobox.com>
Date: Wed, 16 Nov 2022 14:27:34 +0000
Subject: make: changes to suffix substitution in macro expansion

The POSIX standard defines suffix substitution in macro expansion
as taking the form:

   $(string1 [: subst1 =[ subst2 ]])

Since 'subst1' isn't bracketed a value must be supplied.  Enforce
this in POSIX mode.

As a non-POSIX extension an empty 'subst1' is permitted with 'subst2'
being added to all words unconditionally.  If both 'subst1' and
'subst2' are empty the words are returned unchanged.
---
 miscutils/make.c     | 27 ++++++++++++++++++---------
 testsuite/make.tests | 11 +++++++++++
 2 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/miscutils/make.c b/miscutils/make.c
index 1104dfe87..941aa49e3 100644
--- a/miscutils/make.c
+++ b/miscutils/make.c
@@ -913,14 +913,14 @@ skip_macro(const char *s)
  * Returns an allocated string or NULL if the input is unmodified.
  */
 static char *
-modify_words(const char *val, int modifier, size_t lenf,
+modify_words(const char *val, int modifier, size_t lenf, size_t lenr,
 				const char *find_pref, const char *repl_pref,
 				const char *find_suff, const char *repl_suff)
 {
 	char *s, *copy, *word, *sep, *buf = NULL;
 	size_t find_pref_len = 0, find_suff_len = 0;
 
-	if (!modifier && !lenf)
+	if (!modifier && lenf == 0 && lenr == 0)
 		return buf;
 
 	if (find_pref) {
@@ -948,14 +948,18 @@ modify_words(const char *val, int modifier, size_t lenf,
 				word = sep + 1;
 			}
 		}
-		if (lenf) {
+		if (find_pref != NULL || lenf != 0 || lenr != 0) {
 			size_t lenw = strlen(word);
 			// This code implements pattern macro expansions:
 			//    https://austingroupbugs.net/view.php?id=519
 			//
 			// find: <prefix>%<suffix>
 			// example: src/%.c
-			if (lenw >= lenf - 1 && find_pref) {
+			//
+			// For a pattern of the form:
+			//    $(string1:[op]%[os]=[np][%][ns])
+			// lenf is the length of [op]%[os].  So lenf >= 1.
+			if (find_pref != NULL && lenw + 1 >= lenf) {
 				// If prefix and suffix of word match find_pref and
 				// find_suff, then do substitution.
 				if (strncmp(word, find_pref, find_pref_len) == 0 &&
@@ -1011,7 +1015,7 @@ expand_macros(const char *str, int except_dollar)
 	char *find, *replace, *modified;
 	char *expval, *expfind, *find_suff, *repl_suff;
 	char *find_pref = NULL, *repl_pref = NULL;
-	size_t lenf;
+	size_t lenf, lenr;
 	char modifier;
 	struct macro *mp;
 
@@ -1041,11 +1045,13 @@ expand_macros(const char *str, int except_dollar)
 			}
 
 			// Only do suffix replacement or pattern macro expansion
-			// if both ':' and '=' are found.  This is indicated by
-			// lenf != 0.
+			// if both ':' and '=' are found, plus a '%' for the latter.
+			// Suffix replacement is indicated by
+			// find_pref == NULL && (lenf != 0 || lenr != 0);
+			// pattern macro expansion by find_pref != NULL.
 			expfind = NULL;
 			find_suff = repl_suff = NULL;
-			lenf = 0;
+			lenf = lenr = 0;
 			if ((find = find_char(name, ':'))) {
 				*find++ = '\0';
 				expfind = expand_macros(find, FALSE);
@@ -1059,8 +1065,11 @@ expand_macros(const char *str, int except_dollar)
 						if ((repl_suff = strchr(replace, '%')))
 							*repl_suff++ = '\0';
 					} else {
+						if (posix && lenf == 0)
+							error("empty suffix");
 						find_suff = expfind;
 						repl_suff = replace;
+						lenr = strlen(repl_suff);
 					}
 				}
 			}
@@ -1105,7 +1114,7 @@ expand_macros(const char *str, int except_dollar)
 				mp->m_flag = TRUE;
 				expval = expand_macros(mp->m_val, FALSE);
 				mp->m_flag = FALSE;
-				modified = modify_words(expval, modifier, lenf,
+				modified = modify_words(expval, modifier, lenf, lenr,
 								find_pref, repl_pref, find_suff, repl_suff);
 				if (modified)
 					free(expval);
diff --git a/testsuite/make.tests b/testsuite/make.tests
index 8a0f1a7d2..7749bed52 100755
--- a/testsuite/make.tests
+++ b/testsuite/make.tests
@@ -450,6 +450,17 @@ test.b:
 '
 cd .. || exit 1; rm -rf make.tempdir 2>/dev/null
 
+# An empty original suffix indicates that every word should have
+# the new suffix added.  If neither suffix is provided the words
+# remain unchanged.
+testing "make macro expansion and suffix substitution 3" \
+	"make -f -" "src1.c src2.c\nsrc1 src2\n" "" '
+SRCS = src1 src2
+target:
+	@echo $(SRCS:=.c)
+	@echo $(SRCS:=)
+'
+
 # Skip duplicate entries in $? and $^
 mkdir make.tempdir && cd make.tempdir || exit 1
 touch -t 202206171200 file1 file3
-- 
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