make: different treatment for escaped NL in macro in command

Austin Group defect report 1549 has been accepted.  It requires
that an escaped newline inside a macro expansion in a command is
replaced by a space.  Other escaped newlines in commands are
left in place, as before.

2 files changed, 37 insertions, 6 deletions

diff --git a/miscutils/make.c b/miscutils/make.c
index df46256bb..111ab2914 100644
--- a/miscutils/make.c
+++ b/miscutils/make.c
@@ -1401,17 +1401,35 @@ static char *
 process_command(char *s)
 {
         char *t, *u;
+        int len = strlen(s) + 1;
+        char *outside = xzalloc(len);
 
-        // Remove tab following escaped newline.  Stop processing at a
-        // non-escaped newline.
-        for (t = u = s; *u && *u != '\n'; u++) {
-                *t++ = *u;
+        for (t = skip_macro(s); *t; t = skip_macro(t + 1)) {
+                outside[t - s] = 1;
+        }
+
+        // Process escaped newlines.  Stop at first non-escaped newline.
+        for (t = u = s; *u && *u != '\n'; ) {
                 if (u[0] == '\\' && u[1] == '\n') {
-                        *t++ = '\n';
-                        u += (u[2] == '\t') ? 2 : 1;
+                        if (posix || outside[u - s]) {
+                                // Outside macro: remove tab following escaped newline.
+                                *t++ = *u++;
+                                *t++ = *u++;
+                                u += (*u == '\t');
+                        } else {
+                                // Inside macro: replace escaped newline and any leading
+                                // whitespace on the following line with a single space.
+                                u += 2;
+                                while (isspace(*u))
+                                        ++u;
+                                *t++ = ' ';
+                        }
+                } else {
+                        *t++ = *u++;
                 }
         }
         *t = '\0';
+        free(outside);
         return s;
 }
 
diff --git a/testsuite/make.tests b/testsuite/make.tests
index 35d3b7149..8b46faf3c 100755
--- a/testsuite/make.tests
+++ b/testsuite/make.tests
@@ -307,6 +307,19 @@ target: file1 .WAIT file2
 '
 cd .. || exit 1; rm -rf make.tempdir 2>/dev/null
 
+# Escaped newlines inside macro expansions in commands get different
+# treatment than those outside.  In POSIX 2017 the output is 'a b ab'.
+testing "make replace escaped NL in macro in command with space" \
+        "make -f -" \
+        "a b a b\n" "" '
+M=word
+N=${M:word=a\
+b}
+target:
+        @echo ${N} ${M:word=a\
+b}
+'
+
 testing "make double-colon rule" \
         "make -f -" "target1\ntarget2\n" "" '
 target::