From 41f5420db7a911fb0833be693205f4db41f05434 Mon Sep 17 00:00:00 2001

From: Chet Ramey <chet.ramey@case.edu>

Date: Sat, 20 Apr 2019 14:25:52 -0400

Subject: [PATCH] Bash-5.0 patch 5: prevent optimizing forks away too

 aggressively

---

 builtins/evalstring.c | 26 +++++++++++++++++++++++---

 command.h             |  1 +

 execute_cmd.c         |  2 ++

 patchlevel.h          |  2 +-

 4 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/builtins/evalstring.c b/builtins/evalstring.c

index 1496eeec..cadc9bc0 100644

--- a/builtins/evalstring.c

+++ b/builtins/evalstring.c

@@ -100,12 +100,22 @@ should_suppress_fork (command)

 	  ((command->flags & CMD_INVERT_RETURN) == 0));

 }

+int

+can_optimize_connection (command)

+     COMMAND *command;

+{

+  return (*bash_input.location.string == '\0' &&

+	  (command->value.Connection->connector == AND_AND || command->value.Connection->connector == OR_OR || command->value.Connection->connector == ';') &&

+	  command->value.Connection->second->type == cm_simple);

+}

+

 void

 optimize_fork (command)

      COMMAND *command;

 {

   if (command->type == cm_connection &&

-      (command->value.Connection->connector == AND_AND || command->value.Connection->connector == OR_OR) &&

+      (command->value.Connection->connector == AND_AND || command->value.Connection->connector == OR_OR || command->value.Connection->connector == ';') &&

+      (command->value.Connection->second->flags & CMD_TRY_OPTIMIZING) &&

       should_suppress_fork (command->value.Connection->second))

     {

       command->value.Connection->second->flags |= CMD_NO_FORK;

@@ -412,8 +422,18 @@ parse_and_execute (string, from_file, flags)

 		  command->flags |= CMD_NO_FORK;

 		  command->value.Simple->flags |= CMD_NO_FORK;

 		}

-	      else if (command->type == cm_connection)

-		optimize_fork (command);

+

+	      /* Can't optimize forks out here execept for simple commands.

+		 This knows that the parser sets up commands as left-side heavy

+		 (&& and || are left-associative) and after the single parse,

+		 if we are at the end of the command string, the last in a

+		 series of connection commands is

+		 command->value.Connection->second. */

+	      else if (command->type == cm_connection && can_optimize_connection (command))

+		{

+		  command->value.Connection->second->flags |= CMD_TRY_OPTIMIZING;

+		  command->value.Connection->second->value.Simple->flags |= CMD_TRY_OPTIMIZING;

+		}

 #endif /* ONESHOT */

 	      /* See if this is a candidate for $( 

diff --git a/command.h b/command.h

index 32495162..b9e9b669 100644

--- a/command.h

+++ b/command.h

@@ -186,6 +186,7 @@ typedef struct element {

 #define CMD_COPROC_SUBSHELL 0x1000

 #define CMD_LASTPIPE	    0x2000

 #define CMD_STDPATH	    0x4000	/* use standard path for command lookup */

+#define CMD_TRY_OPTIMIZING  0x8000	/* try to optimize this simple command */

 /* What a command looks like. */

 typedef struct command {

diff --git a/execute_cmd.c b/execute_cmd.c

index 8b3c83aa..f1d74bfe 100644

--- a/execute_cmd.c

+++ b/execute_cmd.c

@@ -2767,6 +2767,8 @@ execute_connection (command, asynchronous, pipe_in, pipe_out, fds_to_close)

 	  ((command->value.Connection->connector == OR_OR) &&

 	   (exec_result != EXECUTION_SUCCESS)))

 	{

+	  optimize_fork (command);

+

 	  second = command->value.Connection->second;

 	  if (ignore_return && second)

 	    second->flags |= CMD_IGNORE_RETURN;

diff --git a/patchlevel.h b/patchlevel.h

index c059f0bd..1bc098b8 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 4

+#define PATCHLEVEL 5

 #endif /* _PATCHLEVEL_H_ */

-- 

2.17.2