diff --git a/libstdc++-v3/src/c++98/istream.cc b/libstdc++-v3/src/c++98/istream.cc
index 07ac739c26aad4b2da57966641569289393a03e7..d1b4444ff2b04d3fe2c537cddb12d6ea01a806ca 100644
--- a/libstdc++-v3/src/c++98/istream.cc
+++ b/libstdc++-v3/src/c++98/istream.cc
@@ -112,8 +112,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
basic_istream<char>::
ignore(streamsize __n, int_type __delim)
{
- if (traits_type::eq_int_type(__delim, traits_type::eof()))
- return ignore(__n);
+ {
+ // If conversion to int_type changes the value then __delim does not
+ // correspond to a value of type char_type, and so will never match
+ // a character extracted from the input sequence. Just use ignore(n).
+ const int_type chk_delim = traits_type::to_int_type(__delim);
+ const bool matchable = traits_type::eq_int_type(chk_delim, __delim);
+ if (__builtin_expect(!matchable, 0))
+ return ignore(__n);
+ // Now we know that __delim is a valid char_type value, so it's safe
+ // for the code below to use traits_type::find to search for it.
+ }
_M_gcount = 0;
sentry __cerb(*this, true);
diff --git a/libstdc++-v3/testsuite/27_io/basic_istream/ignore/char/93672.cc b/libstdc++-v3/testsuite/27_io/basic_istream/ignore/char/93672.cc
new file mode 100644
index 0000000000000000000000000000000000000000..96737485b83d6f9c5d3e81b36c05d681e4acc1f5
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_istream/ignore/char/93672.cc
@@ -0,0 +1,101 @@
+// { dg-do run }
+
+#include <sstream>
+#include <limits>
+#include <testsuite_hooks.h>
+
+void
+test_pr93672() // std::basic_istream::ignore hangs if delim MSB is set
+{
+ std::istringstream in(".\xfc..\xfd...\xfe.");
+
+ // This should find '\xfd' even on platforms where char is signed,
+ // because the delimiter is correctly converted to the stream's int_type.
+ in.ignore(100, std::char_traits<char>::to_int_type('\xfc'));
+ VERIFY( in.gcount() == 2 );
+ VERIFY( ! in.eof() );
+
+ // This should work equivalently to traits_type::to_int_type
+ in.ignore(100, (unsigned char)'\xfd');
+ VERIFY( in.gcount() == 3 );
+ VERIFY( ! in.eof() );
+
+ // This only works if char is unsigned.
+ in.ignore(100, '\xfe');
+ if (std::numeric_limits<char>::is_signed)
+ {
+ // When char is signed, '\xfe' != traits_type::to_int_type('\xfe')
+ // so the delimiter does not match the character in the input sequence,
+ // and ignore consumes all input until EOF.
+ VERIFY( in.gcount() == 5 );
+ VERIFY( in.eof() );
+ }
+ else
+ {
+ // When char is unsigned, '\xfe' == to_int_type('\xfe') so the delimiter
+ // matches the character in the input sequence, and doesn't reach EOF.
+ VERIFY( in.gcount() == 4 );
+ VERIFY( ! in.eof() );
+ }
+
+ in.clear();
+ in.str(".a.");
+ in.ignore(100, 'a' + 256); // Should not match 'a'
+ VERIFY( in.gcount() == 3 );
+ VERIFY( in.eof() );
+}
+
+// Custom traits type that inherits all behaviour from std::char_traits<char>.
+struct traits : std::char_traits<char> { };
+
+void
+test_primary_template()
+{
+ // Check that the primary template for std::basic_istream::ignore
+ // works the same as the std::istream::ignore specialization.
+ // The infinite loop bug was never present in the primary template,
+ // because it doesn't use traits_type::find to search the input sequence.
+
+ std::basic_istringstream<char, traits> in(".\xfc..\xfd...\xfe.");
+
+ // This should find '\xfd' even on platforms where char is signed,
+ // because the delimiter is correctly converted to the stream's int_type.
+ in.ignore(100, std::char_traits<char>::to_int_type('\xfc'));
+ VERIFY( in.gcount() == 2 );
+ VERIFY( ! in.eof() );
+
+ // This should work equivalently to traits_type::to_int_type
+ in.ignore(100, (unsigned char)'\xfd');
+ VERIFY( in.gcount() == 3 );
+ VERIFY( ! in.eof() );
+
+ // This only works if char is unsigned.
+ in.ignore(100, '\xfe');
+ if (std::numeric_limits<char>::is_signed)
+ {
+ // When char is signed, '\xfe' != traits_type::to_int_type('\xfe')
+ // so the delimiter does not match the character in the input sequence,
+ // and ignore consumes all input until EOF.
+ VERIFY( in.gcount() == 5 );
+ VERIFY( in.eof() );
+ }
+ else
+ {
+ // When char is unsigned, '\xfe' == to_int_type('\xfe') so the delimiter
+ // matches the character in the input sequence, and doesn't reach EOF.
+ VERIFY( in.gcount() == 4 );
+ VERIFY( ! in.eof() );
+ }
+
+ in.clear();
+ in.str(".a.");
+ in.ignore(100, 'a' + 256); // Should not match 'a'
+ VERIFY( in.gcount() == 3 );
+ VERIFY( in.eof() );
+}
+
+int main()
+{
+ test_pr93672();
+ test_primary_template();
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_istream/ignore/wchar_t/93672.cc b/libstdc++-v3/testsuite/27_io/basic_istream/ignore/wchar_t/93672.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5ce9155e02c568dac6d11aefda6e6be10c03dd6f
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_istream/ignore/wchar_t/93672.cc
@@ -0,0 +1,34 @@
+// { dg-do run }
+
+#include <sstream>
+#include <limits>
+#include <climits>
+#include <testsuite_hooks.h>
+
+// PR 93672 was a bug in std::istream that never affected std::wistream.
+// This test ensures that the bug doesn't get introduced to std::wistream.
+void
+test_pr93672()
+{
+ std::wstring str = L".x..x.";
+ str[1] = (wchar_t)-2;
+ str[4] = (wchar_t)-3;
+ std::wistringstream in(str);
+
+ // This should find the character even on platforms where wchar_t is signed,
+ // because the delimiter is correctly converted to the stream's int_type.
+ in.ignore(100, std::char_traits<wchar_t>::to_int_type((wchar_t)-2));
+ VERIFY( in.gcount() == 2 );
+ VERIFY( ! in.eof() );
+
+ // This also works, because std::char_traits<wchar_t>::to_int_type(wc) is
+ // equivalent to (int_type)wc so using to_int_type isn't needed.
+ in.ignore(100, (wchar_t)-3);
+ VERIFY( in.gcount() == 3 );
+ VERIFY( ! in.eof() );
+}
+
+int main()
+{
+ test_pr93672();
+}