[gcc r12-5878] libstdc++: Implement std::ios_base::noreplace for C++23 [PR59769]
Jonathan Wakely
redi@gcc.gnu.org
Thu Dec 9 23:29:29 GMT 2021
https://gcc.gnu.org/g:a219139e986a4200a9105d7c1fa63735d2945994
commit r12-5878-ga219139e986a4200a9105d7c1fa63735d2945994
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Wed Dec 8 20:58:11 2021 +0000
libstdc++: Implement std::ios_base::noreplace for C++23 [PR59769]
This implements my P2467R0 proposal to support opening an fstream in
exclusive mode. The new constant is also supported pre-C++23 as
std::ios_base::__noreplace.
This proposal hasn't been approved for C++23 yet, but I am confident it
will be, as this is restoring a feture found in pre-ISO C++ iostreams
implementations (and still present in the MSVC library as _Noreplace).
If the proposal fails for C++23 we can remove the ios::noreplace
name and just keep ios::__noreplace as an extension.
libstdc++-v3/ChangeLog:
PR libstdc++/59769
* config/io/basic_file_stdio.cc (fopen_mode): Add support for
exclusive mode.
* include/bits/ios_base.h (_S_noreplace): Define new enumerator.
(ios_base::__noreplace): Define.
(ios_base::noreplace): Define for C++23.
* include/std/version (__cpp_lib_ios_noreplace): Define.
* testsuite/27_io/basic_ofstream/open/char/noreplace.cc: New test.
* testsuite/27_io/basic_ofstream/open/wchar_t/noreplace.cc: New test.
Diff:
---
libstdc++-v3/config/io/basic_file_stdio.cc | 48 ++++++++++++----------
libstdc++-v3/include/bits/ios_base.h | 9 ++++
libstdc++-v3/include/std/version | 1 +
.../27_io/basic_ofstream/open/char/noreplace.cc | 29 +++++++++++++
.../27_io/basic_ofstream/open/wchar_t/noreplace.cc | 29 +++++++++++++
5 files changed, 95 insertions(+), 21 deletions(-)
diff --git a/libstdc++-v3/config/io/basic_file_stdio.cc b/libstdc++-v3/config/io/basic_file_stdio.cc
index ce4a6380ebb..06ee016d016 100644
--- a/libstdc++-v3/config/io/basic_file_stdio.cc
+++ b/libstdc++-v3/config/io/basic_file_stdio.cc
@@ -78,32 +78,38 @@ namespace
out = std::ios_base::out,
trunc = std::ios_base::trunc,
app = std::ios_base::app,
- binary = std::ios_base::binary
+ binary = std::ios_base::binary,
+ noreplace = std::_S_noreplace
};
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 596. 27.8.1.3 Table 112 omits "a+" and "a+b" modes.
- switch (mode & (in|out|trunc|app|binary))
+ switch (mode & (in|out|trunc|app|binary|noreplace))
{
- case ( out ): return "w";
- case ( out |app ): return "a";
- case ( app ): return "a";
- case ( out|trunc ): return "w";
- case (in ): return "r";
- case (in|out ): return "r+";
- case (in|out|trunc ): return "w+";
- case (in|out |app ): return "a+";
- case (in |app ): return "a+";
-
- case ( out |binary): return "wb";
- case ( out |app|binary): return "ab";
- case ( app|binary): return "ab";
- case ( out|trunc |binary): return "wb";
- case (in |binary): return "rb";
- case (in|out |binary): return "r+b";
- case (in|out|trunc |binary): return "w+b";
- case (in|out |app|binary): return "a+b";
- case (in |app|binary): return "a+b";
+ case ( out ): return "w";
+ case ( out |noreplace): return "wx";
+ case ( out|trunc ): return "w";
+ case ( out|trunc |noreplace): return "wx";
+ case ( out |app ): return "a";
+ case ( app ): return "a";
+ case (in ): return "r";
+ case (in|out ): return "r+";
+ case (in|out|trunc ): return "w+";
+ case (in|out|trunc |noreplace): return "w+x";
+ case (in|out |app ): return "a+";
+ case (in |app ): return "a+";
+
+ case ( out |binary ): return "wb";
+ case ( out |binary|noreplace): return "wbx";
+ case ( out |app|binary ): return "ab";
+ case ( app|binary ): return "ab";
+ case ( out|trunc |binary ): return "wb";
+ case (in |binary ): return "rb";
+ case (in|out |binary ): return "r+b";
+ case (in|out|trunc |binary ): return "w+b";
+ case (in|out|trunc |binary|noreplace): return "w+bx";
+ case (in|out |app|binary ): return "a+b";
+ case (in |app|binary ): return "a+b";
default: return 0; // invalid
}
diff --git a/libstdc++-v3/include/bits/ios_base.h b/libstdc++-v3/include/bits/ios_base.h
index d6626d4d26b..5db05524e1c 100644
--- a/libstdc++-v3/include/bits/ios_base.h
+++ b/libstdc++-v3/include/bits/ios_base.h
@@ -116,6 +116,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_S_in = 1L << 3,
_S_out = 1L << 4,
_S_trunc = 1L << 5,
+ _S_noreplace = 1L << 6,
_S_ios_openmode_end = 1L << 16,
_S_ios_openmode_max = __INT_MAX__,
_S_ios_openmode_min = ~__INT_MAX__
@@ -466,6 +467,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
/// Truncate an existing stream when opening. Default for @c ofstream.
static const openmode trunc = _S_trunc;
+ static const openmode __noreplace = _S_noreplace;
+
+#if __cplusplus >= 202100L
+#define __cpp_lib_ios_noreplace 202200L
+ /// Open a file in exclusive mode.
+ static const openmode noreplace = _S_noreplace;
+#endif
+
// 27.4.2.1.5 Type ios_base::seekdir
/**
* @brief This is an enumerated type.
diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index eb612f57c73..23890037b6b 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -296,6 +296,7 @@
#define __cpp_lib_adaptor_iterator_pair_constructor 202106L
#define __cpp_lib_byteswap 202110L
#define __cpp_lib_invoke_r 202106L
+#define __cpp_lib_ios_noreplace 202200L
#define __cpp_lib_is_scoped_enum 202011L
#if __cpp_lib_concepts
# define __cpp_lib_monadic_optional 202110L
diff --git a/libstdc++-v3/testsuite/27_io/basic_ofstream/open/char/noreplace.cc b/libstdc++-v3/testsuite/27_io/basic_ofstream/open/char/noreplace.cc
new file mode 100644
index 00000000000..e39f5928a1f
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_ofstream/open/char/noreplace.cc
@@ -0,0 +1,29 @@
+// { dg-do run }
+
+#include <ios>
+
+#if __cplusplus >= 202200L
+#ifndef __cpp_lib_ios_noreplace
+# error "Feature-test macro for ios::noreplace missing in <ios>"
+#elif __cpp_lib_ios_noreplace < 202200L
+# error "Feature-test macro for ios::noreplace has wrong value in <ios>"
+#endif
+#endif
+
+#include <fstream>
+#include <testsuite_hooks.h>
+
+int main()
+{
+#if __cpp_lib_ios_noreplace
+ std::ios::openmode noreplace = std::ios::noreplace;
+#else
+ std::ios::openmode noreplace = std::ios::__noreplace;
+#endif
+
+ std::ofstream of("noreplace");
+ VERIFY( of.is_open() );
+ of.close();
+ of.open("noreplace", noreplace);
+ VERIFY( ! of.is_open() );
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_ofstream/open/wchar_t/noreplace.cc b/libstdc++-v3/testsuite/27_io/basic_ofstream/open/wchar_t/noreplace.cc
new file mode 100644
index 00000000000..77f11865ac4
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_ofstream/open/wchar_t/noreplace.cc
@@ -0,0 +1,29 @@
+// { dg-do run }
+
+#include <version>
+
+#if __cplusplus >= 202200L
+#ifndef __cpp_lib_ios_noreplace
+# error "Feature-test macro for ios::noreplace missing in <version>"
+#elif __cpp_lib_ios_noreplace < 202200L
+# error "Feature-test macro for ios::noreplace has wrong value in <version>"
+#endif
+#endif
+
+#include <fstream>
+#include <testsuite_hooks.h>
+
+int main()
+{
+#if __cpp_lib_ios_noreplace
+ std::wios::openmode noreplace = std::wios::noreplace;
+#else
+ std::wios::openmode noreplace = std::wios::__noreplace;
+#endif
+
+ std::wofstream of("noreplace");
+ VERIFY( of.is_open() );
+ of.close();
+ of.open("noreplace", noreplace);
+ VERIFY( ! of.is_open() );
+}
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