NaCl docs: mention static libraries for SJLJ

native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst

 ============================
 PNaCl C/C++ Language Support
 ============================
 
 .. contents::
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    :depth: 3
 
 Source language support
@@ skipping 158 matching lines @@
 
 PNaCl and NaCl support ``setjmp`` and ``longjmp`` without any
 restrictions beyond C's.
 
 .. _exception_handling:
 
 C++ Exception Handling
 ======================
 
 PNaCl currently supports C++ exception handling through ``setjmp()`` and
-``longjmp()``, which can be enabled with the ``--pnacl-exceptions=sjlj``
-linker flag. Exceptions are disabled by default so that faster and
-smaller code is generated, and ``throw`` statements are replaced with
-calls to ``abort()``. The usual ``-fno-exceptions`` flag is also
-supported. PNaCl will support full zero-cost exception handling in the
-future.
+``longjmp()``, which can be enabled with the ``--pnacl-exceptions=sjlj`` linker
+flag (set with ``LDFLAGS`` when using Make). Exceptions are disabled by default

[Sam Clegg, 2015/02/19 18:37:47]

Is it a linker flag?  I assumed it was a compiler flag.  If its a linker flag
there is no need to rebuild the libraries (maybe for glibc which uses shared
libraries).

[JF, 2015/02/19 19:15:45]

That's entirely true! Docs updated, thanks for catching this.

+so that faster and smaller code is generated, and ``throw`` statements are
+replaced with calls to ``abort()``. The usual ``-fno-exceptions`` flag is also
+supported, though the default is ``-fexceptions``. PNaCl will support full
+zero-cost exception handling in the future.
+
+.. note:: When using naclports_ or other prebuilt static libraries, you'll want
+          to make sure these libraries are built with the same configuration
+          your library is built with. If you want to use exception handling,
+          then you'll need to rebuild these libraries with exception handling
+          enabled. For naclports, you'll want to modify the port's ``build.sh``.
+
+.. _naclports: https://code.google.com/p/naclports
 
 NaCl supports full zero-cost C++ exception handling.
 
 Inline Assembly
 ===============
 
 Inline assembly isn't supported by PNaCl because it isn't portable. The
 one current exception is the common compiler barrier idiom
 ``asm("":::"memory")``, which gets transformed to a sequentially
 consistent memory barrier (equivalent to ``__sync_synchronize()``). In
@@ skipping 274 matching lines @@
   A similar feature is **thread suspension**: The ability to
   asynchronously suspend and resume a thread and inspect or modify its
   execution state (such as register state).
 
   Neither PNaCl nor NaCl currently support asynchronous interruption
   or suspension of threads.
 
 If PNaCl were to support either of these, the interaction of
 ``volatile`` and atomics with same-thread signal handling would need
 to be carefully detailed.