[libc++] Remove libc++'s own <setjmp.h> header (#68806)

It doesn't seem to do anything useful beyond what the C library header
is doing, so there's no purpose in having one.

Author: ldionne

libcxx/include/CMakeLists.txt

@@ -977,7 +977,6 @@ set(files
   scoped_allocator
   semaphore
   set
-  setjmp.h
   shared_mutex
   source_location
   span

libcxx/include/__std_clang_module

@@ -169,7 +169,6 @@
 #  include <semaphore>
 #endif
 #include <set>
-#include <setjmp.h>
 #if !defined(_LIBCPP_HAS_NO_THREADS)
 #  include <shared_mutex>
 #endif

libcxx/include/csetjmp

@@ -35,14 +35,6 @@ void longjmp(jmp_buf env, int val);
 
 #include <setjmp.h>
 
-#ifndef _LIBCPP_SETJMP_H
-#   error <csetjmp> tried including <setjmp.h> but didn't find libc++'s <setjmp.h> header. \
-          This usually means that your header search paths are not configured properly. \
-          The header search paths should contain the C++ Standard Library headers before \
-          any C Standard Library, and you are probably using compiler flags that make that \
-          not be the case.
-#endif
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif

libcxx/include/module.modulemap.in

@@ -456,10 +456,7 @@ module std_math_h [system] {
   header "math.h"
   export *
 }
-module std_setjmp_h [system] {
-  header "setjmp.h"
-  export *
-}
+// <setjmp.h> provided by C library.
 // <signal.h> provided by C library.
 // FIXME: <stdalign.h> is missing.
 // <stdarg.h> provided by compiler.

libcxx/include/setjmp.h

@@ -7,14 +7,15 @@
 //===----------------------------------------------------------------------===//
 
 // test <setjmp.h>
+//
+// Even though <setjmp.h> is not provided by libc++, we still test that
+// using it with libc++ on the search path will work.
 
 #include <setjmp.h>
 
 #include "test_macros.h"
 
-#ifndef setjmp
-#error setjmp not defined
-#endif
-
 jmp_buf jb;
 ASSERT_SAME_TYPE(void, decltype(longjmp(jb, 0)));
+
+void f() { setjmp(jb); }

libcxx/test/std/depr/depr.c.headers/setjmp_h.compile.pass.cpp

@@ -9,20 +9,28 @@
 // test <csetjmp>
 
 #include <csetjmp>
+#include <cassert>
 #include <type_traits>
 
-#include "test_macros.h"
+int main(int, char**) {
+  std::jmp_buf jb;
 
-#ifndef setjmp
-#error setjmp not defined
-#endif
+  switch (setjmp(jb)) {
+  // First time we set the buffer, the function should return 0
+  case 0:
+    break;
 
-int main(int, char**)
-{
-    std::jmp_buf jb;
-    ((void)jb); // Prevent unused warning
-    static_assert((std::is_same<decltype(std::longjmp(jb, 0)), void>::value),
-                  "std::is_same<decltype(std::longjmp(jb, 0)), void>::value");
+  // If it returned 42, then we're coming from the std::longjmp call below
+  case 42:
+    return 0;
 
-  return 0;
+  // Otherwise, something is wrong
+  default:
+    return 1;
+  }
+
+  std::longjmp(jb, 42);
+  static_assert(std::is_same<decltype(std::longjmp(jb, 0)), void>::value, "");
+
+  return 1;
 }

libcxx/test/std/language.support/support.runtime/csetjmp.pass.cpp

@@ -418,7 +418,6 @@ libcxx/include/regex
 libcxx/include/scoped_allocator
 libcxx/include/semaphore
 libcxx/include/set
-libcxx/include/setjmp.h
 libcxx/include/span
 libcxx/include/__split_buffer
 libcxx/include/sstream
@@ -2725,7 +2724,6 @@ libcxx/test/std/depr/depr.c.headers/inttypes_h.compile.pass.cpp
 libcxx/test/std/depr/depr.c.headers/limits_h.compile.pass.cpp
 libcxx/test/std/depr/depr.c.headers/locale_h.compile.pass.cpp
 libcxx/test/std/depr/depr.c.headers/math_h.pass.cpp
-libcxx/test/std/depr/depr.c.headers/setjmp_h.compile.pass.cpp
 libcxx/test/std/depr/depr.c.headers/signal_h.compile.pass.cpp
 libcxx/test/std/depr/depr.c.headers/stdarg_h.compile.pass.cpp
 libcxx/test/std/depr/depr.c.headers/stdbool_h.compile.pass.cpp
@@ -3941,7 +3939,6 @@ libcxx/test/std/language.support/support.rtti/bad.typeid/bad_typeid.pass.cpp
 libcxx/test/std/language.support/support.rtti/type.info/type_info.equal.pass.cpp
 libcxx/test/std/language.support/support.rtti/type.info/type_info_hash.pass.cpp
 libcxx/test/std/language.support/support.rtti/type.info/type_info.pass.cpp
-libcxx/test/std/language.support/support.runtime/csetjmp.pass.cpp
 libcxx/test/std/language.support/support.runtime/csignal.pass.cpp
 libcxx/test/std/language.support/support.runtime/cstdarg.pass.cpp
 libcxx/test/std/language.support/support.runtime/cstdbool.pass.cpp