Fix various things about SIGINT handling:

* exception handlers are now run with interrupts disabled, which avoids
  many race conditions
* fix some cases where SIGINT only aborts one command and continues the
  script, in particular if a SIGINT causes an EINTR error which trumped the
  interrupt.

Example:
  sh -c 'echo < /some/fifo; echo This should not be printed'
The fifo should not have writers. When pressing ctrl+c to abort the open,
the shell used to continue with the next command.

Example:
  sh -c '/bin/echo < /some/fifo; echo This should not be printed'
Similar. Note, however, that this particular case did not and does not work
in interactive mode with job control enabled.

1 files changed, 13 insertions, 2 deletions

diff --git a/bin/sh/error.c b/bin/sh/error.c
index 0c981a3eff92..72061b8a1bef 100644
--- a/bin/sh/error.c
+++ b/bin/sh/error.c
@@ -73,11 +73,15 @@ static void exverror(int, const char *, va_list) __printf0like(2, 0);
  * Called to raise an exception.  Since C doesn't include exceptions, we
  * just do a longjmp to the exception handler.  The type of exception is
  * stored in the global variable "exception".
+ *
+ * Interrupts are disabled; they should be reenabled when the exception is
+ * caught.
  */
 
 void
 exraise(int e)
 {
+	INTOFF;
 	if (handler == NULL)
 		abort();
 	exception = e;
@@ -138,8 +142,15 @@ onint(void)
 static void
 exverror(int cond, const char *msg, va_list ap)
 {
-	CLEAR_PENDING_INT;
-	INTOFF;
+	/*
+	 * An interrupt trumps an error.  Certain places catch error
+	 * exceptions or transform them to a plain nonzero exit code
+	 * in child processes, and if an error exception can be handled,
+	 * an interrupt can be handled as well.
+	 *
+	 * exraise() will disable interrupts for the exception handler.
+	 */
+	FORCEINTON;
 
 #ifdef DEBUG
 	if (msg)