miyuki created this revision.
[libcxx] Fix basic_stringbuf constructor
The C++ Standard [stringbuf.cons]p1 defines the effects of the basic_stringbuf
constructor that takes ios_base::openmode as follows:
Effects: Constructs an object of class basic_stringbuf, initializing the
base class with basic_streambuf(), and initializing mode with which.
Postconditions: str() == "".
The default constructor of basic_streambuf shall initialize all its
pointer member objects to null pointers [streambuf.cons]p1.
Currently libc++ calls "str(string_type());" in the aforementioned constructor
setting basic_streambuf's pointers to a non-null value.
This patch removes the call (note that the postcondition str() == ""
remains valid because __str_ is default-initialized) and adds a test checking
that the basic_streambuf's pointers are null after construction.
https://reviews.llvm.org/D40707
Files:
include/sstream
test/std/input.output/string.streams/stringbuf/stringbuf.cons/default.pass.cpp
Index:
test/std/input.output/string.streams/stringbuf/stringbuf.cons/default.pass.cpp
===================================================================
---
test/std/input.output/string.streams/stringbuf/stringbuf.cons/default.pass.cpp
+++
test/std/input.output/string.streams/stringbuf/stringbuf.cons/default.pass.cpp
@@ -17,6 +17,21 @@
#include <sstream>
#include <cassert>
+template<typename CharT>
+struct testbuf
+ : std::basic_stringbuf<CharT>
+{
+ void check()
+ {
+ assert(this->eback() == 0);
+ assert(this->gptr() == 0);
+ assert(this->egptr() == 0);
+ assert(this->pbase() == 0);
+ assert(this->pptr() == 0);
+ assert(this->epptr() == 0);
+ }
+};
+
int main()
{
{
@@ -27,4 +42,12 @@
std::wstringbuf buf;
assert(buf.str() == L"");
}
+ {
+ testbuf<char> buf;
+ buf.check();
+ }
+ {
+ testbuf<wchar_t> buf;
+ buf.check();
+ }
}
Index: include/sstream
===================================================================
--- include/sstream
+++ include/sstream
@@ -243,7 +243,6 @@
: __hm_(0),
__mode_(__wch)
{
- str(string_type());
}
template <class _CharT, class _Traits, class _Allocator>
Index: test/std/input.output/string.streams/stringbuf/stringbuf.cons/default.pass.cpp
===================================================================
--- test/std/input.output/string.streams/stringbuf/stringbuf.cons/default.pass.cpp
+++ test/std/input.output/string.streams/stringbuf/stringbuf.cons/default.pass.cpp
@@ -17,6 +17,21 @@
#include <sstream>
#include <cassert>
+template<typename CharT>
+struct testbuf
+ : std::basic_stringbuf<CharT>
+{
+ void check()
+ {
+ assert(this->eback() == 0);
+ assert(this->gptr() == 0);
+ assert(this->egptr() == 0);
+ assert(this->pbase() == 0);
+ assert(this->pptr() == 0);
+ assert(this->epptr() == 0);
+ }
+};
+
int main()
{
{
@@ -27,4 +42,12 @@
std::wstringbuf buf;
assert(buf.str() == L"");
}
+ {
+ testbuf<char> buf;
+ buf.check();
+ }
+ {
+ testbuf<wchar_t> buf;
+ buf.check();
+ }
}
Index: include/sstream
===================================================================
--- include/sstream
+++ include/sstream
@@ -243,7 +243,6 @@
: __hm_(0),
__mode_(__wch)
{
- str(string_type());
}
template <class _CharT, class _Traits, class _Allocator>
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