Systems like FreeBSD's Capsicum and Nuxi CloudABI apply the concept of
capability-based security on the way processes can interact with the
filesystem API. It is no longer possible to interact with the VFS
through calls like open(), unlink(), rename(), etc. Instead, processes
are only allowed to interact with files and directories to which they
have been granted access. The *at() functions can be used for this
purpose.
This change adds a new config switch called
_LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE. If set, all functionality
that requires the global filesystem namespace will be disabled. More
concretely:
- fstream's open() function will be removed.
- cstdio will no longer pull in fopen(), rename(), etc.
- The test suite's get_temp_file_name() will be removed. This will cause
all tests that use the global filesystem namespace to break, but will
at least make all the other tests run (as get_temp_file_name will not
build anyway).
It is important to mention that this change will make fstream rather
useless on those systems for now. Still, I'd rather not have fstream
disabled entirely, as it is of course possible to come up with an
extension for fstream that would allow access to local filesystem
namespaces (e.g., by adding an openat() member function).
Differential revision: http://reviews.llvm.org/D8194
Reviewed by: jroelofs (thanks!)
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@232049 91177308-0d34-0410-b5e6-96231b3b80d8
Remaining characters should be discarded once sync() called. If don’t, garbage
characters can be inserted to the front of external buffer in underflow().
Because underflow() copies remaining characters in external buffer to it’s
front. This results wrong characters insertion when seekpos() or seekoff() is
called.
this line should be inserted in sync() just before return:
__extbufnext_ = __extbufend_ = __extbuf_;
2. sync() should use length() rather than out() to calculate offset.
Reversing iterators and calling out() to calculate offset from behind is
working fine in stateless character encoding. However, in stateful encoding,
escape sequences could differ in length. As a result, out() could return wrong
length.
For example, if we have internal buffer converted from this external sequence:
(capital letters mean escape sequence)
… a a a a B b b b b
out() produces this sequence.
b b b b A a a a a
Because out() inserts escape sequence A rather than B, result sequence doesn't
match to external sequence. A and B could have different lengths, result offset
could be wrong value too.
length() method in codecvt is right for calculating offset, but it counts
offset from the beginning of buffer. So it requires another state member
variable to hold state before conversion.
Fixes http://llvm.org/bugs/show_bug.cgi?id=13667
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@162601 91177308-0d34-0410-b5e6-96231b3b80d8
