Apply comments & add more tests

Author: AlexeySachkov

sycl/cmake/modules/SYCLVersionFromVCS.cmake

@@ -1,15 +1,32 @@
+# Helper utility to generate sycl/version.hpp file which contains various
+# identifiers which can be used to distinguish different builds between each
+# other:
+#
+# __LIBSYCL_TIMESTAMP - timestamp of the latest commit made into sycl/ directory
+# in YYYYMMDD format
+#
+# __SYCL_COMPILER_VERSION - date when configure step was launched in YYYYMMDD
+# format. Deprecated
+#
+# Note: it may not always be the case that CMake configuration step was re-run
+# when a new commits is added and therefore, execute_process won't be re-run and
+# the hash won't be updated. It is not considered to be a problem, because for
+# local incremental builds made during the library/headers development the date
+# doesn't matter much and we can guarantee it to be always correct when we do
+# nightly builds.
 
-# Grab the date of the latest commit
+# Grab the date of the latest commit in sycl folder
 execute_process(
-  COMMAND git log -1 --format=%as # date in YYYY-MM-DD mode
-  WORKING_DIRECTORY ${SYCL_ROOT_SOURCE_DIR}
-  OUTPUT_VARIABLE GIT_COMMIT_DATE_TEMP
+  # date in YYYYMMDD mode, see strftime for reference
+  COMMAND git log -1 --format=%ad --date=format:%Y%m%d -- ${SYCL_ROOT_SOURCE_DIR}
+  OUTPUT_VARIABLE __LIBSYCL_TIMESTAMP
   OUTPUT_STRIP_TRAILING_WHITESPACE
 )
 
-string(REPLACE "-" "" __LIBSYCL_TIMESTAMP ${GIT_COMMIT_DATE_TEMP})
-
 # Legacy thing for backwards compatibility. Use of the current date is not
 # reliable, because we can always make new build from older commits.
 string(TIMESTAMP __SYCL_COMPILER_VERSION "%Y%m%d")
-configure_file("${sycl_src_dir}/version.hpp.in" "${SYCL_INCLUDE_BUILD_DIR}/sycl/version.hpp")
+configure_file(
+  "${sycl_src_dir}/version.hpp.in"
+  "${SYCL_INCLUDE_BUILD_DIR}/sycl/version.hpp"
+)

sycl/test/libsycl-timestamp.cpp

@@ -0,0 +1,9 @@
+// RUN: %clangxx -fsycl -fsyntax-only -Xclang -verify %s
+// expected-no-diagnostics
+
+#include <sycl/sycl.hpp>
+
+#ifndef __LIBSYCL_TIMESTAMP
+#error "__LIBSYCL_TIMESTAMP is expected to be defined by sycl.hpp"
+Some weird code to cause compilation error
+#endif

sycl/unittests/misc/CMakeLists.txt

@@ -4,4 +4,5 @@ add_sycl_unittest(MiscTests SHARED
   CircularBuffer.cpp
   OsUtils.cpp
   PropertyUtils.cpp
+  LibSYCLTimestamp.cpp
 )

sycl/unittests/misc/LibSYCLTimestamp.cpp

@@ -0,0 +1,55 @@
+//==------------------------ LibSYCLTimestamp.cpp --------------------------==//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <sycl/version.hpp>
+
+#include <gtest/gtest.h>
+
+#include <string>
+#include <cctype>
+
+#define _STR(e) #e
+#define STR(e) _STR(e)
+
+TEST(LibSYCLTimestamp, Format) {
+  // __LIBSYCL_TIMESTAMP format is YYYYMMDD
+  std::string Timestamp = STR(__LIBSYCL_TIMESTAMP);
+
+  ASSERT_EQ(Timestamp.size(), 8u);
+
+  for (char C : Timestamp) {
+    ASSERT_TRUE(std::isdigit(C));
+  }
+
+  constexpr size_t Y0 = 0;
+  constexpr size_t Y1 = 1;
+  constexpr size_t M0 = 4;
+  constexpr size_t M1 = 5;
+  constexpr size_t D0 = 6;
+  constexpr size_t D1 = 7;
+
+  // Safe enough test for the next 900+ years
+  ASSERT_EQ(Timestamp[Y0], '2');
+  // Safe enough test for the next 70+ years
+  ASSERT_EQ(Timestamp[Y1], '0');
+
+  ASSERT_TRUE(Timestamp[M0] == '0' || Timestamp[M1] == '1');
+  if (Timestamp[M0] == '1')
+    ASSERT_TRUE(Timestamp[M1] >= '0' && Timestamp[M1] <= '2');
+  ASSERT_FALSE(Timestamp[M0] == '0' && Timestamp[M1] == '0');
+
+  ASSERT_TRUE(Timestamp[D0] >= '0' && Timestamp[D0] <= '3');
+  if (Timestamp[D0] == '3')
+    ASSERT_TRUE(Timestamp[D1] == '0' || Timestamp[D1] == '1');
+  ASSERT_FALSE(Timestamp[D0] == '0' && Timestamp[D1] == '0');
+}
+
+TEST(LibSYCLTimestasmp, BasicAcceptance) {
+  // Date when this feature was introduced
+  ASSERT_TRUE(__LIBSYCL_TIMESTAMP >= 20241128);
+}