[libc][NFC] Remove dependecies on entrypoints from loader tests.

[sivachandra]

Summary

A small collection of utils called osutils has been added. These utils
are now used in loader tests instead of the equivalent entrypoints.
The loader can now be built and tested without depending on any entrypoint.
In a follow up change, the relevent entrypoints will be updated to use the
newly added osutils.

[michaelrj]

lgtm

libc/src/__support/CMakeLists.txt

 
 add_header_library(
   integer_operations
   HDRS
     integer_operations.h
 )
 
 add_subdirectory(FPUtil)
+add_subdirectory(OSUtil)

libc/src/__support/OSUtil/CMakeLists.txt

+add_subdirectory(linux)
+
+add_header_library(
+  osutil
+  HDRS
+    io.h
+    quick_exit.h
+  DEPENDS
+    libc.src.__support.OSUtil.linux.linux_util
+)

libc/src/__support/OSUtil/io.h

+//===---------------- Implementation of IO utils ----------------*- 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_SUPPORT_OSUTIL_IO_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_IO_H
+
+#ifdef __unix__
+#include "linux/io.h"
+#endif
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_IO_H

libc/src/__support/OSUtil/linux/CMakeLists.txt

+add_header_library(
+  linux_util
+  HDRS
+    io.h
+    quick_exit.h
+  DEPENDS
+    libc.config.linux.linux_syscall_h
+    libc.include.sys_syscall
+    libc.src.string.string_utils
+)

libc/src/__support/OSUtil/linux/io.h

+//===-------------- Linux implementation of IO utils ------------*- 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_SUPPORT_OSUTIL_LINUX_IO_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_IO_H
+
+#include "config/linux/syscall.h" // For internal syscall function.
+#include "include/sys/syscall.h"  // For syscall numbers.
+#include "src/string/string_utils.h"
+
+namespace __llvm_libc {
+
+static inline void write_to_stderr(const char *msg) {
+  __llvm_libc::syscall(SYS_write, 2 /* stderr */, msg,
+                       internal::string_length(msg));
+}
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_IO_H

libc/src/__support/OSUtil/linux/quick_exit.h

+//===---------- Linux implementation of a quick exit function ---*- 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_SUPPORT_OSUTIL_LINUX_QUICK_EXIT_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_QUICK_EXIT_H
+
+#include "config/linux/syscall.h" // For internal syscall function.
+#include "include/sys/syscall.h"  // For syscall numbers.
+
+namespace __llvm_libc {
+
+static inline void quick_exit(int status) {
+  for (;;) {
+    __llvm_libc::syscall(SYS_exit_group, status);
+    __llvm_libc::syscall(SYS_exit, status);
+  }
+}
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_QUICK_EXIT_H

libc/src/__support/OSUtil/quick_exit.h

+//===---------- Implementation of a quick exit function ---------*- 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_SUPPORT_OSUTIL_QUICK_EXIT_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_QUICK_EXIT_H
+
+#ifdef __unix__
+#include "linux/quick_exit.h"
+#endif
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_QUICK_EXIT_H

libc/test/loader/linux/CMakeLists.txt

 if(NOT (EXISTS ${LIBC_SOURCE_DIR}/loader/linux/${LIBC_TARGET_ARCHITECTURE}))
   message("Skipping loader tests for target architecture ${LIBC_TARGET_ARCHITECTURE}.")
   return()
 endif()
 
+add_header_library(
+  loader_test
+  HDRS
+    loader_test.h
+  DEPENDS
+    libc.src.__support.OSUtil.osutil
+)
+
 add_loader_test(
   loader_args_test
   SRC
     args_test.cpp
   DEPENDS
+    .loader_test
     libc.loader.linux.crt1
-    libc.src.assert.__assert_fail
-    libc.src.signal.raise
-    libc.src.stdlib._Exit
-    libc.src.stdlib.abort
   ARGS
     1 2 3
   ENV
     FRANCE=Paris
     GERMANY=Berlin
 )
 
 add_loader_test(
   loader_no_envp_test
   SRC
     main_without_envp.cpp
   DEPENDS
+    .loader_test
     libc.loader.linux.crt1
 )
 
 add_loader_test(
   loader_no_args_test
   SRC
     main_without_args.cpp
   DEPENDS
+    .loader_test
     libc.loader.linux.crt1
 )
 
 # TODO: Disableing this test temporarily to investigate why gold fails to link
 # and produce an executable for this test. Test works all fine with ld.bfd.
 #add_loader_test(
 #  loader_tls_test
 #  SRC

libc/test/loader/linux/args_test.cpp

 //===-- Loader test to check args to main ---------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
-#undef NDEBUG
-#include "src/assert/assert.h"
+#include "loader_test.h"
 
 static bool my_streq(const char *lhs, const char *rhs) {
   const char *l, *r;
   for (l = lhs, r = rhs; *l != '\0' && *r != '\0'; ++l, ++r)
     if (*l != *r)
       return false;
 
   return *l == '\0' && *r == '\0';
 }
 
 int main(int argc, char **argv, char **envp) {
-  assert(argc == 4 && "Unexpected argc.");
-  assert(my_streq(argv[1], "1") && "Unexpected argv[1].");
-  assert(my_streq(argv[2], "2") && "Unexpected argv[2].");
-  assert(my_streq(argv[3], "3") && "Unexpected argv[3].");
+  ASSERT_TRUE(argc == 4);
+  ASSERT_TRUE(my_streq(argv[1], "1"));
+  ASSERT_TRUE(my_streq(argv[2], "2"));
+  ASSERT_TRUE(my_streq(argv[3], "3"));
 
   bool found_france = false;
   bool found_germany = false;
   for (; *envp != nullptr; ++envp) {
     if (my_streq(*envp, "FRANCE=Paris"))
       found_france = true;
     if (my_streq(*envp, "GERMANY=Berlin"))
       found_germany = true;
   }
 
-  assert(found_france && found_germany &&
-         "Did not find whats expected in envp.");
+  ASSERT_TRUE(found_france && found_germany);
 
   return 0;
 }

libc/test/loader/linux/loader_test.h

+//===-- Simple checkers for loader tests ------------------------*- 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_LOADER_LINUX_LOADER_TEST_H
+#define LLVM_LIBC_TEST_LOADER_LINUX_LOADER_TEST_H
+
+#include "src/__support/OSUtil/io.h"
+#include "src/__support/OSUtil/quick_exit.h"
+
+#define __AS_STRING(val) #val
+#define __CHECK(file, line, val, should_exit)                                  \
+  if (!(val)) {                                                                \
+    __llvm_libc::write_to_stderr(file ":" __AS_STRING(                         \
+        line) ": Expected '" #val "' to be true, but is false\n");             \
+    if (should_exit)                                                           \
+      __llvm_libc::quick_exit(127);                                            \
+  }
+
+#define EXPECT_TRUE(val) __CHECK(__FILE__, __LINE__, val, false)
+#define ASSERT_TRUE(val) __CHECK(__FILE__, __LINE__, val, true)
+
+#endif // LLVM_LIBC_TEST_LOADER_LINUX_LOADER_TEST_H