make: show location of errors during build

Error messages only displayed the location of an error while the
makefile was being parsed.

Store the location (makefile name and line number) of each command
line.  This allows location information to be displayed in errors
encountered while targets are being built.

Take this Makefile, for example:

target:
	@echo $(hello

Previously this would display:

   make: unterminated variable '$(hello'

Now it shows:

   make: (Makefile:2): unterminated variable '$(hello'

1 files changed, 41 insertions, 15 deletions

diff --git a/miscutils/make.c b/miscutils/make.c
index aedb1c74a..1104dfe87 100644
--- a/miscutils/make.c
+++ b/miscutils/make.c
@@ -149,6 +149,8 @@ struct cmd {
         struct cmd *c_next;             // Next command line
         char *c_cmd;                    // Text of command line
         int c_refcnt;                   // Reference count
+        const char *c_makefile; // Makefile in which command was defined
+        int c_dispno;                   // Line number within makefile
 };
 
 // Macro storage
@@ -229,7 +231,23 @@ static int make(struct name *np, int level);
  */
 
 /*
- * Error handler.  Print message, with line number, and exit.
+ * Print message, with makefile and line number if possible.
+ */
+static void
+vwarning(const char *msg, va_list list)
+{
+        const char *old_applet_name = applet_name;
+
+        if (makefile) {
+                fprintf(stderr, "%s: (%s:%d)", applet_name, makefile, dispno);
+                applet_name = "";
+        }
+        bb_verror_msg(msg, list, NULL);
+        applet_name = old_applet_name;
+}
+
+/*
+ * Error handler.  Print message and exit.
  */
 static void error(const char *msg, ...) NORETURN;
 static void
@@ -237,16 +255,8 @@ error(const char *msg, ...)
 {
         va_list list;
 
-        if (makefile) {
-                const char *num = itoa(dispno);
-                char *s = malloc(strlen(makefile) + strlen(num) + 2);
-                if (s) {
-                        sprintf(s, "%s:%s", makefile, num);
-                        applet_name = s;
-                }
-        }
         va_start(list, msg);
-        bb_verror_msg(msg, list, NULL);
+        vwarning(msg, list);
         va_end(list);
         exit(2);
 }
@@ -265,6 +275,16 @@ error_in_inference_rule(const char *s)
         error("%s in inference rule", s);
 }
 
+static void
+warning(const char *msg, ...)
+{
+        va_list list;
+
+        va_start(list, msg);
+        vwarning(msg, list);
+        va_end(list);
+}
+
 static char *
 auto_concat(const char *s1, const char *s2)
 {
@@ -334,6 +354,8 @@ newcmd(struct cmd **cphead, char *str)
         /*(*cphead)->c_next = NULL; - xzalloc did it */
         (*cphead)->c_cmd = xstrdup(str);
         /*(*cphead)->c_refcnt = 0; */
+        (*cphead)->c_makefile = makefile;
+        (*cphead)->c_dispno = dispno;
 }
 
 static void
@@ -1875,7 +1897,7 @@ remove_target(void)
         if (!dryrun && !print && !precious &&
                         target && !(target->n_flag & (N_PRECIOUS | N_PHONY)) &&
                         unlink(target->n_name) == 0) {
-                bb_error_msg("'%s' removed", target->n_name);
+                warning("'%s' removed", target->n_name);
         }
 }
 
@@ -1891,6 +1913,9 @@ docmds(struct name *np, struct cmd *cp)
         for (; cp; cp = cp->c_next) {
                 uint8_t ssilent, signore, sdomake;
 
+                // Location of command in makefile (for use in error messages)
+                makefile = cp->c_makefile;
+                dispno = cp->c_dispno;
                 opts &= ~OPT_make;      // We want to know if $(MAKE) is expanded
                 q = command = expand_macros(cp->c_cmd, FALSE);
                 ssilent = silent || (np->n_flag & N_SILENT) || dotouch;
@@ -1933,7 +1958,7 @@ docmds(struct name *np, struct cmd *cp)
                                 error("couldn't execute '%s'", q);
                         } else if (status != 0 && !signore) {
                                 if (!doinclude)
-                                        bb_error_msg("failed to build '%s'", np->n_name);
+                                        warning("failed to build '%s'", np->n_name);
 #if !ENABLE_PLATFORM_MINGW32
                                 if (status == SIGINT || status == SIGQUIT)
 #endif
@@ -1946,6 +1971,7 @@ docmds(struct name *np, struct cmd *cp)
                 }
                 free(command);
         }
+        makefile = NULL;
         return estat;
 }
 
@@ -1969,7 +1995,7 @@ touch(struct name *np)
                                         return;
                                 }
                         }
-                        bb_perror_msg("touch %s failed", np->n_name);
+                        warning("touch %s failed", np->n_name);
                 }
         }
 }
@@ -2185,10 +2211,10 @@ make(struct name *np, int level)
                         if (sc_cmd)
                                 estat = make1(np, sc_cmd, oodate, allsrc, dedup, impdep);
                         else if (!doinclude)
-                                bb_error_msg("nothing to be done for %s", np->n_name);
+                                warning("nothing to be done for %s", np->n_name);
                         didsomething = 1;
                 } else if (!doinclude) {
-                        bb_error_msg("'%s' not built due to errors", np->n_name);
+                        warning("'%s' not built due to errors", np->n_name);
                 }
                 free(oodate);
         }