This patch is from upstream glibc after 2.33 and is needed in Guix to
fix glibc-2.33 compilation for riscv64-linux.

From 044e603b698093cf48f6e6229e0b66acf05227e4 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Fri, 19 Feb 2021 13:29:00 +0100
Subject: [PATCH] string: Work around GCC PR 98512 in rawmemchr

---
 string/rawmemchr.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/string/rawmemchr.c b/string/rawmemchr.c
index 59bbeeaa42..b8523118e5 100644
--- a/string/rawmemchr.c
+++ b/string/rawmemchr.c
@@ -22,24 +22,28 @@
 # define RAWMEMCHR __rawmemchr
 #endif
 
+/* The pragmata should be nested inside RAWMEMCHR below, but that
+   triggers GCC PR 98512.  */
+DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (7, 0)
+/* GCC 8 warns about the size passed to memchr being larger than
+   PTRDIFF_MAX; the use of SIZE_MAX is deliberate here.  */
+DIAG_IGNORE_NEEDS_COMMENT (8, "-Wstringop-overflow=");
+#endif
+#if __GNUC_PREREQ (11, 0)
+/* Likewise GCC 11, with a different warning option.  */
+DIAG_IGNORE_NEEDS_COMMENT (11, "-Wstringop-overread");
+#endif
+
 /* Find the first occurrence of C in S.  */
 void *
 RAWMEMCHR (const void *s, int c)
 {
-  DIAG_PUSH_NEEDS_COMMENT;
-#if __GNUC_PREREQ (7, 0)
-  /* GCC 8 warns about the size passed to memchr being larger than
-     PTRDIFF_MAX; the use of SIZE_MAX is deliberate here.  */
-  DIAG_IGNORE_NEEDS_COMMENT (8, "-Wstringop-overflow=");
-#endif
-#if __GNUC_PREREQ (11, 0)
-  /* Likewise GCC 11, with a different warning option.  */
-  DIAG_IGNORE_NEEDS_COMMENT (11, "-Wstringop-overread");
-#endif
   if (c != '\0')
     return memchr (s, c, (size_t)-1);
-  DIAG_POP_NEEDS_COMMENT;
   return (char *)s + strlen (s);
 }
 libc_hidden_def (__rawmemchr)
 weak_alias (__rawmemchr, rawmemchr)
+
+DIAG_POP_NEEDS_COMMENT;
--