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authorJonathan Wakely <jwakely@redhat.com>2021-10-01 21:27:24 +0100
committerJonathan Wakely <jwakely@redhat.com>2021-10-04 15:23:28 +0100
commitcf876562c592193732f869e9f96034a42d0fad89 (patch)
treebea69f3de5d35fa5396f00ad388640f2b82748d2
parentfa3ccf8bfe9940b439d6cc2c38ee8da134b0ff2d (diff)
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libstdc++: Disable std::string{,_view} construction from nullptr (P2166R1)
Implement this C++23 feature. Because construction from a null pointer is undefined, we can implement it for C++11 and up, turning undefined behaviour into a compilation error. libstdc++-v3/ChangeLog: * include/bits/basic_string.h (basic_string(nullptr_t)): Define as deleted. (operator=(nullptr_t)): Likewise. * include/bits/cow_string.h (basic_string(nullptr_t)): Likewise. (operator=(nullptr_t)): Likewise. * include/std/string_view (basic_string_view(nullptr_t)): Likewise. * testsuite/21_strings/basic_string/cons/char/nullptr.cc: New test. * testsuite/21_strings/basic_string_view/cons/char/nonnull.cc: Change dg-warning to dg-error. * testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc: Likewise.
-rw-r--r--libstdc++-v3/include/bits/basic_string.h2
-rw-r--r--libstdc++-v3/include/bits/cow_string.h3
-rw-r--r--libstdc++-v3/include/std/string_view2
-rw-r--r--libstdc++-v3/testsuite/21_strings/basic_string/cons/char/nullptr.cc4
-rw-r--r--libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/nonnull.cc2
-rw-r--r--libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc2
6 files changed, 13 insertions, 2 deletions
diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index 24c454d..68c3884 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -623,6 +623,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
_M_construct(__str.begin(), __str.end());
}
+ basic_string(nullptr_t) = delete;
+ basic_string& operator=(nullptr_t) = delete;
#endif // C++11
/**
diff --git a/libstdc++-v3/include/bits/cow_string.h b/libstdc++-v3/include/bits/cow_string.h
index ba4a8cc..f054012 100644
--- a/libstdc++-v3/include/bits/cow_string.h
+++ b/libstdc++-v3/include/bits/cow_string.h
@@ -667,6 +667,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
else
_M_dataplus._M_p = _S_construct(__str.begin(), __str.end(), __a);
}
+
+ basic_string(nullptr_t) = delete;
+ basic_string& operator=(nullptr_t) = delete;
#endif // C++11
/**
diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view
index d8cbee9..996b03f 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -168,6 +168,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif // C++23
#endif // C++20
+ basic_string_view(nullptr_t) = delete;
+
constexpr basic_string_view&
operator=(const basic_string_view&) noexcept = default;
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/nullptr.cc b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/nullptr.cc
new file mode 100644
index 0000000..fdb24ae
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/cons/char/nullptr.cc
@@ -0,0 +1,4 @@
+// { dg-do compile { target c++11 } }
+#include <string>
+
+std::string s = nullptr; // { dg-error "deleted" "P2166R1" }
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/nonnull.cc
index b33af08..f42f95e 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/nonnull.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/char/nonnull.cc
@@ -25,5 +25,5 @@ test01()
{
std::string_view s((const char*)nullptr); // { dg-warning "\\\[-Wnonnull" }
std::string_view t((char*)nullptr); // { dg-warning "\\\[-Wnonnull" }
- std::string_view u(nullptr); // { dg-warning "\\\[-Wnonnull" }
+ std::string_view u(nullptr); // { dg-error "deleted" }
}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc
index 4c10131..e480f7c 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc
@@ -25,5 +25,5 @@ test01()
{
std::wstring_view s((const wchar_t*)nullptr); // { dg-warning "\\\[-Wnonnull" }
std::wstring_view t((wchar_t*)nullptr); // { dg-warning "\\\[-Wnonnull" }
- std::wstring_view u(nullptr); // { dg-warning "\\\[-Wnonnull" }
+ std::wstring_view u(nullptr); // { dg-error "deleted" }
}