linux-kernel - [PATCH v2] fixdep: use fflush() and ferror() to ensure successful write to files

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Message-Id: <20220225144245.182659-1-masahiroy@kernel.org>
Date:   Fri, 25 Feb 2022 23:42:45 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     David Laight <David.Laight@...LAB.COM>,
        linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH v2] fixdep: use fflush() and ferror() to ensure successful write to files

Checking the return value of (v)printf does not ensure the successful
write to the .cmd file.

Call fflush() and ferror() to make sure that everything has been
written to the file.

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

Changes in v2:
  - add error message

 scripts/basic/fixdep.c | 46 +++++++++++++++++-------------------------
 1 file changed, 19 insertions(+), 27 deletions(-)

diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
index 44e887cff49b..2328f9a641da 100644
--- a/scripts/basic/fixdep.c
+++ b/scripts/basic/fixdep.c
@@ -105,25 +105,6 @@ static void usage(void)
 	exit(1);
 }
 
-/*
- * In the intended usage of this program, the stdout is redirected to .*.cmd
- * files. The return value of printf() must be checked to catch any error,
- * e.g. "No space left on device".
- */
-static void xprintf(const char *format, ...)
-{
-	va_list ap;
-	int ret;
-
-	va_start(ap, format);
-	ret = vprintf(format, ap);
-	if (ret < 0) {
-		perror("fixdep");
-		exit(1);
-	}
-	va_end(ap);
-}
-
 struct item {
 	struct item	*next;
 	unsigned int	len;
@@ -189,7 +170,7 @@ static void use_config(const char *m, int slen)
 
 	define_config(m, slen, hash);
 	/* Print out a dependency path from a symbol name. */
-	xprintf("    $(wildcard include/config/%.*s) \\\n", slen, m);
+	printf("    $(wildcard include/config/%.*s) \\\n", slen, m);
 }
 
 /* test if s ends in sub */
@@ -318,13 +299,13 @@ static void parse_dep_file(char *m, const char *target)
 				 */
 				if (!saw_any_target) {
 					saw_any_target = 1;
-					xprintf("source_%s := %s\n\n",
-						target, m);
-					xprintf("deps_%s := \\\n", target);
+					printf("source_%s := %s\n\n",
+					       target, m);
+					printf("deps_%s := \\\n", target);
 				}
 				is_first_dep = 0;
 			} else {
-				xprintf("  %s \\\n", m);
+				printf("  %s \\\n", m);
 			}
 
 			buf = read_file(m);
@@ -347,8 +328,8 @@ static void parse_dep_file(char *m, const char *target)
 		exit(1);
 	}
 
-	xprintf("\n%s: $(deps_%s)\n\n", target, target);
-	xprintf("$(deps_%s):\n", target);
+	printf("\n%s: $(deps_%s)\n\n", target, target);
+	printf("$(deps_%s):\n", target);
 }
 
 int main(int argc, char *argv[])
@@ -363,11 +344,22 @@ int main(int argc, char *argv[])
 	target = argv[2];
 	cmdline = argv[3];
 
-	xprintf("cmd_%s := %s\n\n", target, cmdline);
+	printf("cmd_%s := %s\n\n", target, cmdline);
 
 	buf = read_file(depfile);
 	parse_dep_file(buf, target);
 	free(buf);
 
+	fflush(stdout);
+
+	/*
+	 * In the intended usage, the stdout is redirected to .*.cmd files.
+	 * Call ferror() to catch errors such as "No space left on device".
+	 */
+	if (ferror(stdout)) {
+		fprintf(stderr, "fixdep: not all data was written to the output\n");
+		exit(1);
+	}
+
 	return 0;
 }
-- 
2.32.0