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.

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