[libc] Make libc_errno point to internal errno for non-public builds.

[sivachandra]

Summary

The macro llvmlibc_errno has also been removed. This change completes
the switch to using a hermetic errno for unit tests.

Fixes #61037

[lntue]

I assume the failed sys/stat tests are fixed with https://reviews.llvm.org/D146004?

[sivachandra]

Rebase

[sivachandra]

In D146005#4191501, @lntue wrote:

I assume the failed sys/stat tests are fixed with https://reviews.llvm.org/D146004?

Yes, that is right. The builds have succeeded after I have rebased.

libc/src/errno/CMakeLists.txt

 add_entrypoint_object(
   errno
   SRCS
     libc_errno.cpp
   HDRS
     libc_errno.h     # Include this
-    llvmlibc_errno.h # DEPRECATED: Will be removed soon
   DEPENDS
     libc.include.errno
 )

libc/src/errno/libc_errno.h

 extern "C" {
 extern thread_local int __llvmlibc_internal_errno;
 } // extern "C"
 
 // TODO: After all of libc/src and libc/test are switched over to use
 // libc_errno, this header file will be "shipped" via an add_entrypoint_object
 // target. At which point libc_errno, should point to __llvmlibc_internal_errno
 // if LIBC_COPT_PUBLIC_PACKAGING is not defined.
-#define libc_errno errno
+#define libc_errno __llvm_libc::__llvmlibc_internal_errno
 
 } // namespace __llvm_libc
 #endif
 
 #endif // LLVM_LIBC_SRC_ERRNO_LLVMLIBC_ERRNO_H

libc/src/errno/libc_errno.cpp

 //===-- Implementation of errno -------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 namespace __llvm_libc {
 
 extern "C" {
+#ifdef LIBC_COPT_PUBLIC_PACKAGING
 // TODO: Declare __llvmlibc_errno only under LIBC_COPT_PUBLIC_PACKAGING and
 // __llvmlibc_internal_errno otherwise.
-//
 // In overlay mode, this will be an unused thread local variable as libc_errno
 // will resolve to errno from the system libc's errno.h. In full build mode
 // however, libc_errno will resolve to this thread local variable via the errno
 // macro defined in LLVM libc's public errno.h header file.
 // TODO: Use a macro to distinguish full build and overlay build which can be
 //       used to exclude __llvmlibc_errno under overlay build.
 thread_local int __llvmlibc_errno;
+#else
 thread_local int __llvmlibc_internal_errno;
+#endif
 } // extern "C"
 
 } // namespace __llvm_libc

libc/src/errno/llvmlibc_errno.h

-//===-- Implementation header for errno -------------------------*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_LIBC_SRC_ERRNO_LLVMLIBC_ERRNO_H
-#define LLVM_LIBC_SRC_ERRNO_LLVMLIBC_ERRNO_H
-
-#include <errno.h>
-
-// DEPRECATED: Use libc_errno from libc_errno.h instead. This macro is only
-// present to facilitate gradual transition (as in, in multiple simple patches)
-// to libc_errno.
-// TODO: After all of libc/src and libc/test is switched over to use libc_errno,
-// remove this macro and header file.
-#define llvmlibc_errno errno
-
-#endif // LLVM_LIBC_SRC_ERRNO_LLVMLIBC_ERRNO_H

libc/test/CMakeLists.txt

 add_subdirectory(UnitTest)
 
 if(LLVM_LIBC_FULL_BUILD AND NOT
   (LIBC_TARGET_ARCHITECTURE_IS_GPU OR LIBC_TARGET_OS_IS_BAREMETAL))
   add_subdirectory(IntegrationTest)
 endif()
 
 add_header_library(
   errno_setter_matcher
   HDRS
     ErrnoSetterMatcher.h
+  DEPENDS
+    libc.src.errno.errno
 )
 
 add_custom_target(check-libc)
 add_custom_target(libc-unit-tests)
 add_dependencies(check-libc libc-unit-tests)
 
 add_custom_target(exhaustive-check-libc)
 add_custom_target(libc-long-running-tests)

libc/test/ErrnoSetterMatcher.h

 //===-- ErrnoSetterMatcher.h ------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_LIBC_TEST_ERRNOSETTERMATCHER_H
 #define LLVM_LIBC_TEST_ERRNOSETTERMATCHER_H
 
+#include "src/errno/libc_errno.h"
 #include "test/UnitTest/Test.h"
 
-#include <errno.h>
 #include <string.h>
 
 namespace __llvm_libc {
 namespace testing {
 
 namespace internal {
 
 template <typename T> class ErrnoSetterMatcher : public Matcher<T> {
void explainError(testutils::StreamWrapper &OS) override {
     else
       OS << "Correct value " << ExpectedReturn
          << " was returned\nBut errno was unexpectely set to "
          << strerror(ActualErrno) << ".\n";
   }
 
   bool match(T Got) {
     ActualReturn = Got;
-    ActualErrno = errno;
-    errno = 0;
+    ActualErrno = libc_errno;
+    libc_errno = 0;
     return Got == ExpectedReturn && ActualErrno == ExpectedErrno;
   }
 };
 
 } // namespace internal
 
 namespace ErrnoSetterMatcher {