Make support for thread-unsafe C functions optional.

One of the aspects of CloudABI is that it aims to help you write code
that is thread-safe out of the box. This is very important if you want
to write libraries that are easy to reuse. For CloudABI we decided to
not provide the thread-unsafe functions. So far this is working out
pretty well, as thread-unsafety issues are detected really early on.

The following patch adds a knob to libc++,
_LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS, that can be set to disable
thread-unsafe functions that can easily be avoided in practice. The
following functions are not thread-safe:

- <clocale>: locale handles should be preferred over setlocale().
- <cstdlib>: mbrlen(), mbrtowc() and wcrtomb() should be preferred over
  their non-restartable counterparts.
- <ctime>: asctime(), ctime(), gmtime() and localtime() are not
  thread-safe. The first two are also deprecated by POSIX.

Differential Revision:	http://reviews.llvm.org/D8703
Reviewed by:	marshall

llvm-svn: 240527

10 files changed, 90 insertions, 2 deletions

diff --git a/libcxx/test/std/depr/depr.c.headers/stdlib_h.pass.cpp b/libcxx/test/std/depr/depr.c.headers/stdlib_h.pass.cpp
index 98b19c6eb56..47e1527fb17 100644
--- a/libcxx/test/std/depr/depr.c.headers/stdlib_h.pass.cpp
+++ b/libcxx/test/std/depr/depr.c.headers/stdlib_h.pass.cpp
@@ -71,12 +71,14 @@ int main()
     static_assert((std::is_same<decltype(div(0,0)), div_t>::value), "");
     static_assert((std::is_same<decltype(ldiv(0L,0L)), ldiv_t>::value), "");
     static_assert((std::is_same<decltype(lldiv(0LL,0LL)), lldiv_t>::value), "");
-    static_assert((std::is_same<decltype(mblen("",0)), int>::value), "");
     wchar_t* pw = 0;
     const wchar_t* pwc = 0;
     char* pc = 0;
+#ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
+    static_assert((std::is_same<decltype(mblen("",0)), int>::value), "");
     static_assert((std::is_same<decltype(mbtowc(pw,"",0)), int>::value), "");
     static_assert((std::is_same<decltype(wctomb(pc,L' ')), int>::value), "");
+#endif
     static_assert((std::is_same<decltype(mbstowcs(pw,"",0)), size_t>::value), "");
     static_assert((std::is_same<decltype(wcstombs(pc,pwc,0)), size_t>::value), "");
 }
diff --git a/libcxx/test/std/depr/depr.c.headers/string_h.pass.cpp b/libcxx/test/std/depr/depr.c.headers/string_h.pass.cpp
index fc7f65d4288..afc784f74b8 100644
--- a/libcxx/test/std/depr/depr.c.headers/string_h.pass.cpp
+++ b/libcxx/test/std/depr/depr.c.headers/string_h.pass.cpp
@@ -41,7 +41,9 @@ int main()
     static_assert((std::is_same<decltype(strrchr(cp, 0)), char*>::value), "");
     static_assert((std::is_same<decltype(strspn(cpc, cpc)), size_t>::value), "");
     static_assert((std::is_same<decltype(strstr(cp, cpc)), char*>::value), "");
+#ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
     static_assert((std::is_same<decltype(strtok(cp, cpc)), char*>::value), "");
+#endif
     static_assert((std::is_same<decltype(memset(vp, 0, s)), void*>::value), "");
     static_assert((std::is_same<decltype(strerror(0)), char*>::value), "");
     static_assert((std::is_same<decltype(strlen(cpc)), size_t>::value), "");
diff --git a/libcxx/test/std/language.support/support.runtime/cstdlib.pass.cpp b/libcxx/test/std/language.support/support.runtime/cstdlib.pass.cpp
index e14e70e34e4..073949122b0 100644
--- a/libcxx/test/std/language.support/support.runtime/cstdlib.pass.cpp
+++ b/libcxx/test/std/language.support/support.runtime/cstdlib.pass.cpp
@@ -75,12 +75,14 @@ int main()
     static_assert((std::is_same<decltype(std::div(0LL,0LL)), std::lldiv_t>::value), "");
     static_assert((std::is_same<decltype(std::ldiv(0L,0L)), std::ldiv_t>::value), "");
     static_assert((std::is_same<decltype(std::lldiv(0LL,0LL)), std::lldiv_t>::value), "");
-    static_assert((std::is_same<decltype(std::mblen("",0)), int>::value), "");
     wchar_t* pw = 0;
     const wchar_t* pwc = 0;
     char* pc = 0;
+#ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
+    static_assert((std::is_same<decltype(std::mblen("",0)), int>::value), "");
     static_assert((std::is_same<decltype(std::mbtowc(pw,"",0)), int>::value), "");
     static_assert((std::is_same<decltype(std::wctomb(pc,L' ')), int>::value), "");
+#endif
     static_assert((std::is_same<decltype(std::mbstowcs(pw,"",0)), std::size_t>::value), "");
     static_assert((std::is_same<decltype(std::wcstombs(pc,pwc,0)), std::size_t>::value), "");
 }
diff --git a/libcxx/test/std/language.support/support.runtime/ctime.pass.cpp b/libcxx/test/std/language.support/support.runtime/ctime.pass.cpp
index 495d6eb2c66..8c5d2811d8a 100644
--- a/libcxx/test/std/language.support/support.runtime/ctime.pass.cpp
+++ b/libcxx/test/std/language.support/support.runtime/ctime.pass.cpp
@@ -30,10 +30,12 @@ int main()
     static_assert((std::is_same<decltype(std::difftime(t,t)), double>::value), "");
     static_assert((std::is_same<decltype(std::mktime(&tm)), std::time_t>::value), "");
     static_assert((std::is_same<decltype(std::time(&t)), std::time_t>::value), "");
+#ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
     static_assert((std::is_same<decltype(std::asctime(&tm)), char*>::value), "");
     static_assert((std::is_same<decltype(std::ctime(&t)), char*>::value), "");
     static_assert((std::is_same<decltype(std::gmtime(&t)), std::tm*>::value), "");
     static_assert((std::is_same<decltype(std::localtime(&t)), std::tm*>::value), "");
+#endif
     char* c1 = 0;
     const char* c2 = 0;
     static_assert((std::is_same<decltype(std::strftime(c1,s,c2,&tm)), std::size_t>::value), "");
diff --git a/libcxx/test/std/localization/c.locales/clocale.pass.cpp b/libcxx/test/std/localization/c.locales/clocale.pass.cpp
index 3b3e933c551..a90725bfa36 100644
--- a/libcxx/test/std/localization/c.locales/clocale.pass.cpp
+++ b/libcxx/test/std/localization/c.locales/clocale.pass.cpp
@@ -12,6 +12,8 @@
 #include <clocale>
 #include <type_traits>
 
+#ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
+
 #ifndef LC_ALL
 #error LC_ALL not defined
 #endif
@@ -36,6 +38,8 @@
 #error LC_TIME not defined
 #endif
 
+#endif // !_LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
+
 #ifndef NULL
 #error NULL not defined
 #endif
@@ -43,6 +47,8 @@
 int main()
 {
     std::lconv lc;
+#ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
     static_assert((std::is_same<decltype(std::setlocale(0, "")), char*>::value), "");
+#endif
     static_assert((std::is_same<decltype(std::localeconv()), std::lconv*>::value), "");
 }
diff --git a/libcxx/test/std/strings/c.strings/cstring.pass.cpp b/libcxx/test/std/strings/c.strings/cstring.pass.cpp
index 5ed7e6cd11a..20f4050cfbd 100644
--- a/libcxx/test/std/strings/c.strings/cstring.pass.cpp
+++ b/libcxx/test/std/strings/c.strings/cstring.pass.cpp
@@ -46,7 +46,9 @@ int main()
     static_assert((std::is_same<decltype(std::strspn(cpc, cpc)), std::size_t>::value), "");
 //    static_assert((std::is_same<decltype(std::strstr(cpc, cpc)), const char*>::value), "");
     static_assert((std::is_same<decltype(std::strstr(cp, cpc)), char*>::value), "");
+#ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
     static_assert((std::is_same<decltype(std::strtok(cp, cpc)), char*>::value), "");
+#endif
     static_assert((std::is_same<decltype(std::memset(vp, 0, s)), void*>::value), "");
     static_assert((std::is_same<decltype(std::strerror(0)), char*>::value), "");
     static_assert((std::is_same<decltype(std::strlen(cpc)), std::size_t>::value), "");
diff --git a/libcxx/test/std/utilities/date.time/asctime.thread-unsafe.fail.cpp b/libcxx/test/std/utilities/date.time/asctime.thread-unsafe.fail.cpp
new file mode 100644
index 00000000000..3a9749e21c5
--- /dev/null
+++ b/libcxx/test/std/utilities/date.time/asctime.thread-unsafe.fail.cpp
@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: libcpp-has-no-thread-unsafe-c-functions
+
+#include <ctime>
+
+int main() {
+    // asctime is not thread-safe.
+    std::time_t t = 0;
+    std::asctime(&t);
+}
diff --git a/libcxx/test/std/utilities/date.time/ctime.thread-unsafe.fail.cpp b/libcxx/test/std/utilities/date.time/ctime.thread-unsafe.fail.cpp
new file mode 100644
index 00000000000..cd246c63152
--- /dev/null
+++ b/libcxx/test/std/utilities/date.time/ctime.thread-unsafe.fail.cpp
@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: libcpp-has-no-thread-unsafe-c-functions
+
+#include <ctime>
+
+int main() {
+    // ctime is not thread-safe.
+    std::time_t t = 0;
+    std::ctime(&t);
+}
diff --git a/libcxx/test/std/utilities/date.time/gmtime.thread-unsafe.fail.cpp b/libcxx/test/std/utilities/date.time/gmtime.thread-unsafe.fail.cpp
new file mode 100644
index 00000000000..a6debcbd98d
--- /dev/null
+++ b/libcxx/test/std/utilities/date.time/gmtime.thread-unsafe.fail.cpp
@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: libcpp-has-no-thread-unsafe-c-functions
+
+#include <ctime>
+
+int main() {
+    // gmtime is not thread-safe.
+    std::time_t t = 0;
+    std::gmtime(&t);
+}
diff --git a/libcxx/test/std/utilities/date.time/localtime.thread-unsafe.fail.cpp b/libcxx/test/std/utilities/date.time/localtime.thread-unsafe.fail.cpp
new file mode 100644
index 00000000000..c9e55c8fd3a
--- /dev/null
+++ b/libcxx/test/std/utilities/date.time/localtime.thread-unsafe.fail.cpp
@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: libcpp-has-no-thread-unsafe-c-functions
+
+#include <ctime>
+
+int main() {
+    // localtime is not thread-safe.
+    std::time_t t = 0;
+    std::localtime(&t);
+}