While adding the new C++17 overloads taking filesystem paths to
<fstream> I noticed that ofstream uses out|trunc for the default
arguments instead of out as the stadnard says. The effect is the same,
but my preference would be to do what the standard says. Is there a
good reason for deviating from what the standard says?
Although the out|trunc default arguments have no difference in
behaviour from just using out, the comments saying
"Calls @c std::basic_filebuf::open(__s,__mode|out|trunc)"
are definitely wrong. That would not be a conforming behaviour.
Also, I think we can remove the comments saying to use c_str() as
fstreams accept std::string arguments since C++11.
Any comments?
diff --git a/libstdc++-v3/include/std/fstream b/libstdc++-v3/include/std/fstream
index 52830945fe2..db41a697085 100644
--- a/libstdc++-v3/include/std/fstream
+++ b/libstdc++-v3/include/std/fstream
@@ -487,9 +487,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @param __mode Open file in specified mode (see std::ios_base).
*
* @c ios_base::in is automatically included in @a __mode.
- *
- * Tip: When using std::string to hold the filename, you must use
- * .c_str() before passing it to this constructor.
*/
explicit
basic_ifstream(const char* __s, ios_base::openmode __mode = ios_base::in)
@@ -587,9 +584,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*
* Calls @c std::basic_filebuf::open(s,__mode|in). If that function
* fails, @c failbit is set in the stream's error state.
- *
- * Tip: When using std::string to hold the filename, you must use
- * .c_str() before passing it to this constructor.
*/
void
open(const char* __s, ios_base::openmode __mode = ios_base::in)
@@ -687,15 +681,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @param __s Null terminated string specifying the filename.
* @param __mode Open file in specified mode (see std::ios_base).
*
- * @c ios_base::out | @c ios_base::trunc is automatically included in
- * @a __mode.
- *
- * Tip: When using std::string to hold the filename, you must use
- * .c_str() before passing it to this constructor.
+ * @c ios_base::out is automatically included in @a __mode.
*/
explicit
basic_ofstream(const char* __s,
- ios_base::openmode __mode = ios_base::out|ios_base::trunc)
+ ios_base::openmode __mode = ios_base::out)
: __ostream_type(), _M_filebuf()
{
this->init(&_M_filebuf);
@@ -708,12 +698,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @param __s std::string specifying the filename.
* @param __mode Open file in specified mode (see std::ios_base).
*
- * @c ios_base::out | @c ios_base::trunc is automatically included in
- * @a __mode.
+ * @c ios_base::out is automatically included in @a __mode.
*/
explicit
basic_ofstream(const std::string& __s,
- ios_base::openmode __mode = ios_base::out|ios_base::trunc)
+ ios_base::openmode __mode = ios_base::out)
: __ostream_type(), _M_filebuf()
{
this->init(&_M_filebuf);
@@ -789,15 +778,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @param __s The name of the file.
* @param __mode The open mode flags.
*
- * Calls @c std::basic_filebuf::open(__s,__mode|out|trunc). If that
+ * Calls @c std::basic_filebuf::open(__s,__mode|out). If that
* function fails, @c failbit is set in the stream's error state.
- *
- * Tip: When using std::string to hold the filename, you must use
- * .c_str() before passing it to this constructor.
*/
void
- open(const char* __s,
- ios_base::openmode __mode = ios_base::out | ios_base::trunc)
+ open(const char* __s, ios_base::openmode __mode = ios_base::out)
{
if (!_M_filebuf.open(__s, __mode | ios_base::out))
this->setstate(ios_base::failbit);
@@ -813,12 +798,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @param __s The name of the file.
* @param __mode The open mode flags.
*
- * Calls @c std::basic_filebuf::open(s,mode|out|trunc). If that
+ * Calls @c std::basic_filebuf::open(s,mode|out). If that
* function fails, @c failbit is set in the stream's error state.
*/
void
- open(const std::string& __s,
- ios_base::openmode __mode = ios_base::out | ios_base::trunc)
+ open(const std::string& __s, ios_base::openmode __mode = ios_base::out)
{
if (!_M_filebuf.open(__s, __mode | ios_base::out))
this->setstate(ios_base::failbit);
@@ -894,9 +878,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @brief Create an input/output file stream.
* @param __s Null terminated string specifying the filename.
* @param __mode Open file in specified mode (see std::ios_base).
- *
- * Tip: When using std::string to hold the filename, you must use
- * .c_str() before passing it to this constructor.
*/
explicit
basic_fstream(const char* __s,
@@ -993,9 +974,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*
* Calls @c std::basic_filebuf::open(__s,__mode). If that
* function fails, @c failbit is set in the stream's error state.
- *
- * Tip: When using std::string to hold the filename, you must use
- * .c_str() before passing it to this constructor.
*/
void
open(const char* __s,
