linux-kernel - [PATCH v2 4/4] modpost: remove unreachable code after fatal()

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Message-Id: <20231203094934.1908270-4-masahiroy@kernel.org>
Date:   Sun,  3 Dec 2023 18:49:34 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>, Tom Rix <trix@...hat.com>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH v2 4/4] modpost: remove unreachable code after fatal()

Now compilers can recognize fatal() never returns.

While GCC 4.5 dropped support for -Wunreachable-code, Clang is capable
of detecting the unreachable code.

  $ make HOSTCC=clang HOSTCFLAGS=-Wunreachable-code-return
      [snip]
    HOSTCC  scripts/mod/modpost.o
  scripts/mod/modpost.c:520:11: warning: 'return' will never be executed [-Wunreachable-code-return]
                          return 0;
                                 ^
  scripts/mod/modpost.c:477:10: warning: 'return' will never be executed [-Wunreachable-code-return]
                  return 0;
                         ^
  2 warnings generated.

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Reviewed-by: Nathan Chancellor <nathan@...nel.org>
---

Changes in v2:
  - Change the patch order
  - Update the commit description and add warning example.

 scripts/mod/modpost.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 3233946fa5f6..e2bc180cecc8 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -476,11 +476,9 @@ static int parse_elf(struct elf_info *info, const char *filename)
 		fatal("%s: not relocatable object.", filename);
 
 	/* Check if file offset is correct */
-	if (hdr->e_shoff > info->size) {
+	if (hdr->e_shoff > info->size)
 		fatal("section header offset=%lu in file '%s' is bigger than filesize=%zu\n",
 		      (unsigned long)hdr->e_shoff, filename, info->size);
-		return 0;
-	}
 
 	if (hdr->e_shnum == SHN_UNDEF) {
 		/*
@@ -518,12 +516,11 @@ static int parse_elf(struct elf_info *info, const char *filename)
 		const char *secname;
 		int nobits = sechdrs[i].sh_type == SHT_NOBITS;
 
-		if (!nobits && sechdrs[i].sh_offset > info->size) {
+		if (!nobits && sechdrs[i].sh_offset > info->size)
 			fatal("%s is truncated. sechdrs[i].sh_offset=%lu > sizeof(*hrd)=%zu\n",
 			      filename, (unsigned long)sechdrs[i].sh_offset,
 			      sizeof(*hdr));
-			return 0;
-		}
+
 		secname = secstrings + sechdrs[i].sh_name;
 		if (strcmp(secname, ".modinfo") == 0) {
 			if (nobits)
-- 
2.40.1