string(TIMESTAMP): Fix unset TZ
The logic added by commit v3.6.0-rc1~338^2 (CMake: Extend TIMESTAMP
sub-commands with new unix time format specifier, 2016-02-16) to restore
the `TZ` environment variable does not properly handle the case in which
the variable was originally not set. Unset the variable in this case.
Fixes: #18431
diff --git a/Source/cmTimestamp.cxx b/Source/cmTimestamp.cxx
index 14cf6e9..da5d21e 100644
--- a/Source/cmTimestamp.cxx
+++ b/Source/cmTimestamp.cxx
@@ -96,7 +96,7 @@
// From Linux timegm() manpage.
std::string tz_old;
- cmSystemTools::GetEnv("TZ", tz_old);
+ bool const tz_was_set = cmSystemTools::GetEnv("TZ", tz_old);
tz_old = "TZ=" + tz_old;
// The standard says that "TZ=" or "TZ=[UNRECOGNIZED_TZ]" means UTC.
@@ -109,7 +109,17 @@
time_t result = mktime(&tm);
+# ifdef CMAKE_BUILD_WITH_CMAKE
+ if (tz_was_set) {
+ cmSystemTools::PutEnv(tz_old);
+ } else {
+ cmSystemTools::UnsetEnv("TZ");
+ }
+# else
+ // No UnsetEnv during bootstrap. This is good enough for CMake itself.
cmSystemTools::PutEnv(tz_old);
+ static_cast<void>(tz_was_set);
+# endif
tzset();
