Hi
Following this report I had a closer look to this debug-dependent
behavior which I agree about.
I have added some checks to 2.cc as shown in the patch. Initially the
test was failing because:
/home/fdt/dev/gcc/git/libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/2.cc:45:
void test02(): Assertion 'old != istrb_eos' failed.
This was coming from the __old._M_c = _M_sbuf->sbumpc() line in the
post-increment operator. The post-increment is supposed to return a copy
of the current iterator which this assignment is compromising. So I try
to remove the assignment and test failed later:
/home/fdt/dev/gcc/git/libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/2.cc:104:
void test02(): Assertion 'c == slit01[i]' failed.
However, run in debug mode, it worked fine.
The test is failing in normal mode because the iterator instantiation
doesn't read the streambuf and without the previous __old._M_c
assignment _M_c is still pointing to eos. In debug mode, _M_at_eof()
initialize the iterator and so it work nicely.
So for those reasons I would like to propose attached patch.
Additionally it gets rid of the mutable usage. And I also remove a
useless noexcept qualification on the defaulted copy constructor.
François
On 01/09/2017 11:10, Jonathan Wakely wrote:
On 24/08/17 12:57 +0300, Petr Ovtchenkov wrote:
Explicit do sgetc from associated streambuf. Avoid debug-dependent
sgetc (within _M_at_eof()):
__glibcxx_requires_cond(!_M_at_eof(),
_M_message(__gnu_debug::__msg_inc_istreambuf)
._M_iterator(*this));
Increment operators not require not-eof precoditions.
Don't unlink associated streambuf if eof detected (in _M_get).
Clean logic in postfix increment operator.
I find it very hard to understand the reasons for this patch. What
you've written above is too terse for me.
Are you fixing a bug? If so, do you have a testcase that demonstrates
the problem, and is fixed by these changes?
Is this just refactoring, without changing behaviour?
Finally, and very importantly, do you have a copyright assignment for
changes to GCC? See https://gcc.gnu.org/contribute.html#legal
diff --git a/libstdc++-v3/include/bits/streambuf_iterator.h b/libstdc++-v3/include/bits/streambuf_iterator.h
index f0451b1..27d0725 100644
--- a/libstdc++-v3/include/bits/streambuf_iterator.h
+++ b/libstdc++-v3/include/bits/streambuf_iterator.h
@@ -94,8 +94,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// the "end of stream" iterator value.
// NB: This implementation assumes the "end of stream" value
// is EOF, or -1.
- mutable streambuf_type* _M_sbuf;
- mutable int_type _M_c;
+ streambuf_type* _M_sbuf;
+ int_type _M_c;
public:
/// Construct end of input stream iterator.
@@ -103,18 +103,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
: _M_sbuf(0), _M_c(traits_type::eof()) { }
#if __cplusplus >= 201103L
- istreambuf_iterator(const istreambuf_iterator&) noexcept = default;
+ istreambuf_iterator(const istreambuf_iterator&) = default;
~istreambuf_iterator() = default;
#endif
/// Construct start of input stream iterator.
istreambuf_iterator(istream_type& __s) _GLIBCXX_USE_NOEXCEPT
- : _M_sbuf(__s.rdbuf()), _M_c(traits_type::eof()) { }
+ : _M_sbuf(__s.rdbuf()), _M_c(traits_type::eof())
+ {
+ if (_M_sbuf)
+ _M_get();
+ }
/// Construct start of streambuf iterator.
istreambuf_iterator(streambuf_type* __s) _GLIBCXX_USE_NOEXCEPT
- : _M_sbuf(__s), _M_c(traits_type::eof()) { }
+ : _M_sbuf(__s), _M_c(traits_type::eof())
+ {
+ if (_M_sbuf)
+ _M_get();
+ }
/// Return the current character pointed to by iterator. This returns
/// streambuf.sgetc(). It cannot be assigned. NB: The result of
@@ -122,28 +130,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
char_type
operator*() const
{
+ int_type __c = _M_get();
+
#ifdef _GLIBCXX_DEBUG_PEDANTIC
// Dereferencing a past-the-end istreambuf_iterator is a
// libstdc++ extension
- __glibcxx_requires_cond(!_M_at_eof(),
+ __glibcxx_requires_cond(!_S_at_eof(__c),
_M_message(__gnu_debug::__msg_deref_istreambuf)
._M_iterator(*this));
#endif
- return traits_type::to_char_type(_M_get());
+ return traits_type::to_char_type(__c);
}
/// Advance the iterator. Calls streambuf.sbumpc().
istreambuf_iterator&
operator++()
{
- __glibcxx_requires_cond(!_M_at_eof(),
+ __glibcxx_requires_cond(_M_sbuf,
_M_message(__gnu_debug::__msg_inc_istreambuf)
._M_iterator(*this));
- if (_M_sbuf)
- {
- _M_sbuf->sbumpc();
- _M_c = traits_type::eof();
- }
+ _M_sbuf->sbumpc();
+ _M_get();
return *this;
}
@@ -151,16 +158,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
istreambuf_iterator
operator++(int)
{
- __glibcxx_requires_cond(!_M_at_eof(),
- _M_message(__gnu_debug::__msg_inc_istreambuf)
- ._M_iterator(*this));
-
istreambuf_iterator __old = *this;
- if (_M_sbuf)
- {
- __old._M_c = _M_sbuf->sbumpc();
- _M_c = traits_type::eof();
- }
+ ++(*this);
return __old;
}
@@ -176,26 +175,31 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
int_type
_M_get() const
{
- const int_type __eof = traits_type::eof();
- int_type __ret = __eof;
+ if (!_S_at_eof(_M_c))
+ return _M_c;
+
if (_M_sbuf)
- {
- if (!traits_type::eq_int_type(_M_c, __eof))
- __ret = _M_c;
- else if (!traits_type::eq_int_type((__ret = _M_sbuf->sgetc()),
- __eof))
- _M_c = __ret;
- else
- _M_sbuf = 0;
- }
- return __ret;
+ return _M_sbuf->sgetc();
+ return _M_c;
+ }
+
+ void
+ _M_get()
+ {
+ _M_c = _M_sbuf->sgetc();
+ if (_S_at_eof(_M_c))
+ _M_sbuf = 0;
}
bool
_M_at_eof() const
+ { return _S_at_eof(_M_get()); }
+
+ static bool
+ _S_at_eof(int_type __c)
{
const int_type __eof = traits_type::eof();
- return traits_type::eq_int_type(_M_get(), __eof);
+ return traits_type::eq_int_type(__c, __eof);
}
};
diff --git a/libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/2.cc b/libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/2.cc
index b81f4d4..498dc1b 100644
--- a/libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/2.cc
+++ b/libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/2.cc
@@ -25,9 +25,7 @@
void test02(void)
{
-
typedef std::istreambuf_iterator<char> cistreambuf_iter;
- typedef cistreambuf_iter::streambuf_type cstreambuf_type;
const char slit01[] = "playa hermosa, liberia, guanacaste";
std::string str01(slit01);
std::istringstream istrs00(str01);
@@ -35,10 +33,18 @@ void test02(void)
// ctor sanity checks
cistreambuf_iter istrb_it01(istrs00);
- cistreambuf_iter istrb_it02;
- std::string tmp(istrb_it01, istrb_it02);
+ cistreambuf_iter istrb_eos;
+ VERIFY( istrb_it01 != istrb_eos );
+
+ std::string tmp(istrb_it01, istrb_eos);
VERIFY( tmp == str01 );
+ VERIFY( istrb_it01 != istrb_eos );
+ VERIFY( *istrb_it01 == 'p' );
+ cistreambuf_iter old = istrb_it01++;
+ VERIFY( old != istrb_eos );
+ VERIFY( istrb_it01 == istrb_eos );
+
cistreambuf_iter istrb_it03(0);
cistreambuf_iter istrb_it04;
VERIFY( istrb_it03 == istrb_it04 );
