Due to the way make is designed, not being able to read a makefile

is basically silent.

Record errors due to missing permissions and other oddities, and display them
when we error out due to lack of targets, as a quality-of-life diagnostic.

Based on a remark from sthen@, with some feedback and tweaks from op@

okay op@, kn@

4 files changed, 65 insertions, 7 deletions

diff --git a/usr.bin/make/engine.c b/usr.bin/make/engine.c
index 410dcd0af27..d1967eab92a 100644
--- a/usr.bin/make/engine.c
+++ b/usr.bin/make/engine.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: engine.c,v 1.70 2021/10/25 19:54:29 kn Exp $ */
+/*	$OpenBSD: engine.c,v 1.71 2023/05/30 04:42:21 espie Exp $ */
 /*
  * Copyright (c) 2012 Marc Espie.
  *
@@ -84,6 +84,7 @@
 #include "extern.h"
 #include "lst.h"
 #include "timestamp.h"
+#include "main.h"
 #include "make.h"
 #include "pathnames.h"
 #include "error.h"
@@ -210,6 +211,7 @@ node_failure(GNode *gn)
 		fflush(stdout);
 	else {
 		print_errors();
+		dump_unreadable();
 		Punt(NULL);
 	}
 }
diff --git a/usr.bin/make/main.c b/usr.bin/make/main.c
index 64ea5d27509..93b38671e25 100644
--- a/usr.bin/make/main.c
+++ b/usr.bin/make/main.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: main.c,v 1.129 2023/01/17 13:03:22 kn Exp $ */
+/*	$OpenBSD: main.c,v 1.130 2023/05/30 04:42:21 espie Exp $ */
 /*	$NetBSD: main.c,v 1.34 1997/03/24 20:56:36 gwr Exp $	*/
 
 /*
@@ -87,6 +87,8 @@ bool 		ignoreErrors;	/* -i flag */
 bool 		beSilent;	/* -s flag */
 bool		dumpData;	/* -p flag */
 
+static LIST 	unreadable;
+
 struct dirs {
 	char *current;
 	char *object;
@@ -826,6 +828,48 @@ main(int argc, char **argv)
 		return 0;
 }
 
+struct unreadable {
+	char *fname;
+	int errcode;
+};
+
+void
+dump_unreadable(void)
+{
+	struct unreadable *u;
+
+	if (Lst_IsEmpty(&unreadable))
+		return;
+
+	fprintf(stderr, "Makefile(s) that couldn't be read:\n");
+
+	while ((u = Lst_Pop(&unreadable))) {
+		fprintf(stderr, "\t%s: %s\n", u->fname, strerror(u->errcode));
+		free(u->fname);
+		free(u);
+	}
+}
+
+static FILE *
+open_makefile(const char *fname)
+{
+	FILE *stream;
+	struct unreadable *u;
+
+	stream = fopen(fname, "r");
+	if (stream != NULL)
+		return stream;
+
+	if (errno != ENOENT) {
+		u = emalloc(sizeof *u);
+		u->fname = estrdup(fname);
+		u->errcode = errno;
+		Lst_AtEnd(&unreadable, u);
+	}
+
+	return NULL;
+}
+
 /*-
  * ReadMakefile  --
  *	Open and parse the given makefile.
@@ -848,14 +892,14 @@ ReadMakefile(void *p, void *q)
 		Var_Set("MAKEFILE", "");
 		Parse_File(estrdup("(stdin)"), stdin);
 	} else {
-		if ((stream = fopen(fname, "r")) != NULL)
+		if ((stream = open_makefile(fname)) != NULL)
 			goto found;
 		/* if we've chdir'd, rebuild the path name */
 		if (d->current != d->object && *fname != '/') {
 			char *path;
 
 			path = Str_concat(d->current, fname, '/');
-			if ((stream = fopen(path, "r")) == NULL)
+			if ((stream = open_makefile(path)) == NULL)
 				free(path);
 			else {
 				fname = path;
@@ -866,7 +910,14 @@ ReadMakefile(void *p, void *q)
 		name = Dir_FindFile(fname, userIncludePath);
 		if (!name)
 			name = Dir_FindFile(fname, systemIncludePath);
-		if (!name || !(stream = fopen(name, "r")))
+		if (!name)
+			return false;
+		/* do not try to open a file we already have, so that
+		 * dump_unreadable() yields non-confusing results.
+		 */
+		if (strcmp(name, fname) == 0)
+			return false;
+		if ((stream = open_makefile(name)) == NULL)
 			return false;
 		fname = name;
 		/*
diff --git a/usr.bin/make/main.h b/usr.bin/make/main.h
index 035de86e602..4106c60daf7 100644
--- a/usr.bin/make/main.h
+++ b/usr.bin/make/main.h
@@ -1,6 +1,6 @@
 #ifndef MAIN_H
 #define MAIN_H
-/*	$OpenBSD: main.h,v 1.6 2020/01/13 14:51:50 espie Exp $ */
+/*	$OpenBSD: main.h,v 1.7 2023/05/30 04:42:21 espie Exp $ */
 
 /*
  * Copyright (c) 2001 Marc Espie.
@@ -41,4 +41,8 @@ extern Lst	create;
 /* set_notparallel(): used to influence running mode from parse.c */
 extern void set_notparallel(void);
 
+/* dump_unreadable: in case of some errors, dump makefile names
+ * we found but are unable to read.
+ */
+extern void dump_unreadable(void);
 #endif
diff --git a/usr.bin/make/parse.c b/usr.bin/make/parse.c
index 1b29df2300b..19f7c83e46f 100644
--- a/usr.bin/make/parse.c
+++ b/usr.bin/make/parse.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: parse.c,v 1.134 2021/03/06 08:31:42 espie Exp $	*/
+/*	$OpenBSD: parse.c,v 1.135 2023/05/30 04:42:21 espie Exp $	*/
 /*	$NetBSD: parse.c,v 1.29 1997/03/10 21:20:04 christos Exp $	*/
 
 /*
@@ -1696,6 +1696,7 @@ void
 Parse_MainName(Lst listmain)	/* result list */
 {
 	if (mainNode == NULL) {
+		dump_unreadable();
 		Punt("no target to make.");
 		/*NOTREACHED*/
 	} else if (mainNode->type & OP_DOUBLEDEP) {