Changeset a35a3d8 in mainline for uspace/lib/c/generic/setjmp.c

Timestamp:

2018-03-12T17:13:46Z (7 years ago)

Author:

GitHub <noreply@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

b127e4af

Parents:

f3d47c97

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2018-03-12 17:13:46)

git-committer:

GitHub <noreply@…> (2018-03-12 17:13:46)

Message:

Turn context_save/context_restore into standard setjmp/longjmp. (#24)

Turn context_save()/context_restore() into semi-standard __setjmp()/__longjmp().

The original context_* functions are similar to setjmp()/longjmp(), except that the return value is more restricted for the former, and with inverted meaning. This commit adopts the standard return value semantics and acknowledges that these functions are "standard setjmp()/longjmp() with additional implementation-specific properties" by changing the name. The only divergence from the standard is that __longjmp() causes __setjmp() to return its value unchanged, even if it is zero. This is just to avoid extra assembly, and longjmp() checks this in C.

Note that the original use of context_save()/context_restore() to implement context switching in fibril implementation has already been delegated to context_create()/context_swap(), which provide more natural control flow.

File:

• uspace/lib/c/generic/setjmp.c (modified) (2 diffs)

uspace/lib/c/generic/setjmp.c

@@ -1 +1 @@
 /*
  * Copyright (c) 2013 Vojtech Horky
+ * Copyright (c) 2018 CZ.NIC, z.s.p.o.
  * All rights reserved.
  *
@@ -30 +31 @@
  * @{
  */
-/** @file Long jump implementation.
- *
- * Implementation inspired by Jiri Zarevucky's code from
- * http://bazaar.launchpad.net/~zarevucky-jiri/helenos/stdc/revision/1544/uspace/lib/posix/setjmp.h
- */
 
 #include <setjmp.h>
 #include <context.h>
 
-// TODO: setjmp/longjmp are basically a stronger version of
-// context_save/context_restore. It would be preferable to turn
-// those two into setjmp/longjmp (all it would need is preserving the
-// return value).
-
-/**
- * Restore environment previously stored by setjmp.
- *
- * This function never returns.
- *
- * @param env Variable with the environment previously stored by call
- * to setjmp.
- * @param val Value to fake when returning from setjmp (0 is transformed to 1).
- */
-void longjmp(jmp_buf env, int val) {
-        env[0].return_value = (val == 0) ? 1 : val;
-        context_restore(&env[0].context);
+/** Standard function implementation. */
+void longjmp(jmp_buf env, int val)
+{
+        /* __longjmp defined in assembly doesn't "correct" the value. */
+        __longjmp(env, val == 0 ? 1 : val);
 }