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FFI: Clarify callback docs.

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This commit is contained in:
Mike Pall 2012-11-07 23:20:50 +01:00
parent 2156925b9b
commit 74feb2534c
1 changed files with 7 additions and 6 deletions
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doc/ext_ffi_semantics.html
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@ -943,9 +943,10 @@ C function is blacklisted for compilation.
<p>
However, this heuristic may fail under specific circumstances: e.g. a
message polling function might not run Lua callbacks right away and the call
gets JIT-compiled. If it later happens to call back into Lua, you'll get a
VM PANIC with the message <tt>"bad callback"</tt>. Then you'll need to
manually turn off JIT-compilation with
gets JIT-compiled. If it later happens to call back into Lua (e.g. a rarely
invoked error callback), you'll get a VM PANIC with the message
<tt>"bad callback"</tt>. Then you'll need to manually turn off
JIT-compilation with
<a href="ext_jit.html#jit_onoff_func"><tt>jit.off()</tt></a> for the
surrounding Lua function that invokes such a message polling function (or
similar).
@ -1038,9 +1039,9 @@ of existing C&nbsp;APIs. E.g. callback performance is irrelevant for a
GUI application, which waits for user input most of the time, anyway.
</p>
<p>
For new designs <b>avoid push-style APIs</b> (C&nbsp;function repeatedly
calling a callback for each result). Instead <b>use pull-style APIs</b>
(call a C&nbsp;function repeatedly to get a new result). Calls from Lua
For new designs <b>avoid push-style APIs</b>: a C&nbsp;function repeatedly
calling a callback for each result. Instead <b>use pull-style APIs</b>:
call a C&nbsp;function repeatedly to get a new result. Calls from Lua
to C via the FFI are much faster than the other way round. Most well-designed
libraries already use pull-style APIs (read/write, get/put).
</p>