>>>>> "Axel" == axel-4eJtQOnFJqFBDgjK7y7TUQ
>>>>> <axel-4ejtqonfjqfbdgjk7y7...@public.gmane.org> writes:
Axel> I'm talking actual crashes, and I don't know how we would fix the
Axel> text formatter. I'm glancing at
Axel>
http://mxr.mozilla.org/mozilla-central/source/xpcom/glue/nsTextFormatter.cpp#778,
Axel> and I had no idea how to fix the C++ API there.
Axel> bug 1133554#c2 is a bug where we got it wrong in en-US, too. Doesn't
Axel> crash, but produces undesirable results.
Axel> Note, folks using the stringbundle.formatStringFromName just use a
Axel> wstring array. The only code paths affected are those that get the
Axel> string, and explicitly call into nsTextFormatter from c++.
I think the best answer for C++ is to write a compiler plugin to do
format checking.
GCC already has code to check that a format string matches the
arguments. However, it can't be applied in several places in the tree
because:
* Various printf-likes in the tree extend the list of formats.
For example, JS uses %hs to print a char16_t*.
(And nsTextFormatter uses %S for this same thing, oops.)
* The in-tree printf-likes sometimes use the same format characters as
printf to mean different things. For example, nspr uses %l to mean
32-bit, whereas printf uses it to mean sizeof(long).
* Some printf-likes, like nsTextFormatter, use a char16_t* as the format
string.
There are GCC bugs open about all of these.
There's also the issue of looking up the format string in a message
catalog. GCC has support for this, too, but I don't know offhand
whether it can handle the approach used here.
It's possible to fix all these things in the compilers. The advantage
of a plugin is that nobody has to wait for a compiler upgrade to use it
to find the bugs.
I think it's worth doing. Before I learned about the various problems,
I took a stab at using the GCC format attributes, and amidst all the
nit-picking there are some genuine bugs.
Tom
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