From a5f4367d2aaabfcad67eb7382bf83ee0aead1f35 Mon Sep 17 00:00:00 2001
From: Chet Ramey <chet.ramey@case.edu>
Date: Tue, 15 Sep 2026 11:12:23 -0400
Subject: [PATCH] Bash-5.3 patch 16: accommodate macOS dynamic pipe sizing,
 avoiding hangs

---
 configure    |  2 +-
 configure.ac |  2 +-
 general.c    | 21 +++++++++++++++++++++
 general.h    |  1 +
 patchlevel.h |  2 +-
 redir.c      | 23 +++++++++++++++++++++++
 6 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index a28a3fcf..a0ff9162 100755
--- a/configure
+++ b/configure
@@ -23133,7 +23133,7 @@ hpux*)		LOCAL_CFLAGS="-DHPUX -DTGETENT_BROKEN -DTGETFLAG_BROKEN" ;;
 dgux*)		LOCAL_CFLAGS=-D_DGUX_SOURCE; LOCAL_LIBS=-ldgc ;;
 isc*)		LOCAL_CFLAGS=-Disc386 ;;
 rhapsody*)	LOCAL_CFLAGS=-DRHAPSODY ;;
-darwin*)	LOCAL_CFLAGS=-DMACOSX ;;
+darwin*)	LOCAL_CFLAGS="-DMACOSX -DPIPESIZE_DYNAMIC" ;;
 sco3.2v5*)	LOCAL_CFLAGS="-b elf -DWAITPID_BROKEN -DPATH_MAX=1024" ;;
 sco3.2v4*)	LOCAL_CFLAGS="-DMUST_UNBLOCK_CHLD -DPATH_MAX=1024" ;;
 sco3.2*)	LOCAL_CFLAGS=-DMUST_UNBLOCK_CHLD ;;
diff --git a/configure.ac b/configure.ac
index 5a76267e..146f5d68 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1209,7 +1209,7 @@ hpux*)		LOCAL_CFLAGS="-DHPUX -DTGETENT_BROKEN -DTGETFLAG_BROKEN" ;;
 dgux*)		LOCAL_CFLAGS=-D_DGUX_SOURCE; LOCAL_LIBS=-ldgc ;;
 isc*)		LOCAL_CFLAGS=-Disc386 ;;
 rhapsody*)	LOCAL_CFLAGS=-DRHAPSODY ;;
-darwin*)	LOCAL_CFLAGS=-DMACOSX ;;
+darwin*)	LOCAL_CFLAGS="-DMACOSX -DPIPESIZE_DYNAMIC" ;;
 sco3.2v5*)	LOCAL_CFLAGS="-b elf -DWAITPID_BROKEN -DPATH_MAX=1024" ;;
 sco3.2v4*)	LOCAL_CFLAGS="-DMUST_UNBLOCK_CHLD -DPATH_MAX=1024" ;;
 sco3.2*)	LOCAL_CFLAGS=-DMUST_UNBLOCK_CHLD ;;
diff --git a/general.c b/general.c
index aeffda5c..c8442efa 100644
--- a/general.c
+++ b/general.c
@@ -595,6 +595,27 @@ sh_unset_nodelay_mode (int fd)
   return 0;
 }
 
+int
+sh_setnodelay (int fd)
+{
+  int flags;
+
+  if ((flags = fcntl (fd, F_GETFL, 0)) < 0)
+    return -1;
+
+  /* This is defined to O_NDELAY in filecntl.h if O_NONBLOCK is not present
+     and O_NDELAY is defined. */
+#ifdef O_NONBLOCK
+  flags |= O_NONBLOCK;
+#endif
+
+#ifdef O_NDELAY
+  flags |= O_NDELAY;
+#endif
+
+  return (fcntl (fd, F_SETFL, flags));
+}
+
 /* Just a wrapper for the define in include/filecntl.h */
 int
 sh_setclexec (int fd)
diff --git a/general.h b/general.h
index 5b1eac08..91425b8c 100644
--- a/general.h
+++ b/general.h
@@ -317,6 +317,7 @@ extern int line_isblank (const char *);
 extern int assignment (const char *, int);
 
 extern int sh_unset_nodelay_mode (int);
+extern int sh_setnodelay (int);
 extern int sh_setclexec (int);
 extern int sh_validfd (int);
 extern int fd_ispipe (int);
diff --git a/patchlevel.h b/patchlevel.h
index 13c6c07d..09d848fc 100644
--- a/patchlevel.h
+++ b/patchlevel.h
@@ -25,6 +25,6 @@
    regexp `^#define[ 	]*PATCHLEVEL', since that's what support/mkversion.sh
    looks for to find the patch level (for the sccs version string). */
 
-#define PATCHLEVEL 15
+#define PATCHLEVEL 16
 
 #endif /* _PATCHLEVEL_H_ */
diff --git a/redir.c b/redir.c
index 343536b7..08d92fca 100644
--- a/redir.c
+++ b/redir.c
@@ -472,7 +472,30 @@ here_document_to_fd (WORD_DESC *redirectee, enum r_instruction ri)
 	}
 #endif
 
+#if defined (PIPESIZE_DYNAMIC)
+      /* If we can't count on the pipe size determined at compile time to be
+	 constant across systems, define PIPESIZE_DYNAMIC in configure.ac.
+	 We set the pipe's write end to be non-blocking, try to write, and
+	 fall back to a temp file on error. */
+      if (sh_setnodelay (herepipe[1]) < 0)
+	{
+	  close (herepipe[0]);
+	  close (herepipe[1]);
+	  goto use_tempfile;
+	}
+#endif
+      
       r = heredoc_write (herepipe[1], document, document_len);
+
+#if defined (PIPESIZE_DYNAMIC)
+      if (r == ENOSPC || r == EAGAIN)
+	{
+	  close (herepipe[0]);
+	  close (herepipe[1]);
+	  goto use_tempfile;
+	}
+#endif
+	  
       if (document != redirectee->word)
 	free (document);
       close (herepipe[1]);