The chrono parsing code failed to check for errors when parsing input to
match %z. The expected input is [+-]hh[mm] but if we read less than two
valid digits for the hh or mm parts we didn't set failbit in the stream,
and used the -1 error values returned for each bad digit in the offset
value. This resulted in a "successful" parse that produced a value like
-11h or -11min for the time zone offset.
libstdc++-v3/ChangeLog:
PR libstdc++/125369
* include/bits/chrono_io.h (__detail::_Parser::operator()):
Check for errors when parsing digits for a %z format.
* testsuite/std/time/parse/125369.cc: New test.
---
Tested x86_64-linux.
This should be backported to gcc-14/15/16.
libstdc++-v3/include/bits/chrono_io.h | 17 +++--
.../testsuite/std/time/parse/125369.cc | 65 +++++++++++++++++++
2 files changed, 78 insertions(+), 4 deletions(-)
create mode 100644 libstdc++-v3/testsuite/std/time/parse/125369.cc
diff --git a/libstdc++-v3/include/bits/chrono_io.h
b/libstdc++-v3/include/bits/chrono_io.h
index 1fe50ad79e05..f840f54e9112 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -5234,8 +5234,13 @@ namespace __detail
else
{
// Read hh
- __hh = 10 * _S_try_read_digit(__is, __err);
- __hh += _S_try_read_digit(__is, __err);
+ auto __d1 = _S_try_read_digit(__is, __err);
+ auto __d2 = _S_try_read_digit(__is, __err);
+ if (__d1 >= 0 && __d2 >= 0) [[likely]]
+ __hh = 10 * __d1 + __d2;
+ else
+ __err |= ios_base::failbit;
+
}
if (__is_failed(__err))
@@ -5269,8 +5274,12 @@ namespace __detail
int_least32_t __mm = 0;
if (__read_mm)
{
- __mm = 10 * _S_try_read_digit(__is, __err);
- __mm += _S_try_read_digit(__is, __err);
+ auto __d1 = _S_try_read_digit(__is, __err);
+ auto __d2 = _S_try_read_digit(__is, __err);
+ if (__d1 >= 0 && __d2 >= 0) [[likely]]
+ __mm = 10 * __d1 + __d2;
+ else
+ __err |= ios_base::failbit;
}
if (!__is_failed(__err))
diff --git a/libstdc++-v3/testsuite/std/time/parse/125369.cc
b/libstdc++-v3/testsuite/std/time/parse/125369.cc
new file mode 100644
index 000000000000..719c56dc9282
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/time/parse/125369.cc
@@ -0,0 +1,65 @@
+// { dg-do run { target c++20 } }
+
+#include <chrono>
+#include <sstream>
+#include <testsuite_hooks.h>
+
+using namespace std::chrono;
+
+const std::string input = "2026-05-18 15:26:48 ";
+const std::string fmt = "%F %T %";
+sys_seconds ss;
+minutes offset{};
+std::string abbrev;
+
+void
+test_parse_z()
+{
+ for (auto suffix : {"Z", "+", "+Z", "-A", "+1Z", "+010", "+010Z"})
+ {
+ std::istringstream in{input + suffix};
+ from_stream(in, (fmt + "z").c_str(), ss, &abbrev, &offset);
+
+ VERIFY( in.fail() );
+ VERIFY( ss == sys_seconds(0s) );
+ VERIFY( offset == 0min );
+ VERIFY( abbrev.empty() );
+ }
+}
+
+void
+test_parse_Ez()
+{
+ for (auto suffix : {"Z", "+", "-", "+01:", "+01:X"})
+ {
+ std::istringstream in{input + suffix};
+ from_stream(in, (fmt + "Ez").c_str(), ss, &abbrev, &offset);
+
+ VERIFY( in.fail() );
+ VERIFY( ss == sys_seconds(0s) );
+ VERIFY( offset == 0min );
+ VERIFY( abbrev.empty() );
+ }
+}
+
+void
+test_parse_Oz()
+{
+ for (auto suffix : {"Z", "+", "-", "+01:", "+01:X"})
+ {
+ std::istringstream in{input + suffix};
+ from_stream(in, (fmt + "Oz").c_str(), ss, &abbrev, &offset);
+
+ VERIFY( in.fail() );
+ VERIFY( ss == sys_seconds(0s) );
+ VERIFY( offset == 0min );
+ VERIFY( abbrev.empty() );
+ }
+}
+
+int main()
+{
+ test_parse_z();
+ test_parse_Ez();
+ test_parse_Oz();
+}
--
2.54.0
