sc_version_string: Use temporary names resilient against parallel builds

In #359 I identify a race condition between multiple parallel invocations of cmake, which can arise naturally during ctests. Now that the file contents will not change without an intervening git commit, it is sufficient to ensure that the parallel invocations use distinct temporary file names with high probability.
sc_version_string: omit the date and time when testing
2017-08-21 08:31:05 -05:00 · 2017-08-21 08:31:00 -05:00 · 2017-08-19 17:12:28 -04:00 · 2017-08-19 15:41:33 -04:00 · 2017-08-15 06:50:56 -05:00
2 changed files with 9 additions and 5 deletions
--- a/cmake/SC_Config_Headers.cmake
+++ b/cmake/SC_Config_Headers.cmake
@ -80,7 +80,7 @@ std::cout << \"1s is \"<< std::chrono::duration_cast<std::chrono::milliseconds>(
  set( TEST_NULLPTR "
 #include <cstddef>
 std::nullptr_t f() {return nullptr;}
-int main() {return !!f();}
+int main() {return !(f() == f());}
  " )
  cmake_push_check_state()
  if( UNIX )
--- a/cmake/sc_version_string.cmake
+++ b/cmake/sc_version_string.cmake
@ -8,6 +8,7 @@
 # http://www.cmake.org/pipermail/cmake/2009-February/027014.html

 set(SC_IS_SUBBUILD "@SC_IS_SUBBUILD@")
+set(SC_ENABLE_TESTING "@SC_ENABLE_TESTING@")

 set(SC_VERSION_HEADER "${BINARY_DIR}/include/sc_version_string.h")

@ -47,7 +48,9 @@ string(REPLACE "\n" "" GIT_COMMIT_ID ${GIT_COMMIT_ID})
 #once cmake_minimum_required is >= 2.8.11, we can use TIMESTAMP:
 #string(TIMESTAMP date_time_string)

-if(UNIX)
+if(SC_ENABLE_TESTING)
+  set (date_time_string "NA - disabled for testing")
+elseif(UNIX)
  execute_process(COMMAND date "+%d %b %Y %H:%M" OUTPUT_VARIABLE date_time_string OUTPUT_STRIP_TRAILING_WHITESPACE)
 elseif(WIN32)
  execute_process(COMMAND cmd /c date /t OUTPUT_VARIABLE currentDate OUTPUT_STRIP_TRAILING_WHITESPACE)
@ -75,9 +78,10 @@ set(header_string "/* sc_version_string.h - written by cmake. Changes will be lo
 )

 #don't update the file unless somethig changed
-file(WRITE ${SC_VERSION_HEADER}.tmp ${header_string})
-execute_process(COMMAND ${CMAKE_COMMAND} -E copy_if_different ${SC_VERSION_HEADER}.tmp ${SC_VERSION_HEADER})
-execute_process(COMMAND ${CMAKE_COMMAND} -E remove ${SC_VERSION_HEADER}.tmp)
+string(RANDOM tmpsuffix)
+file(WRITE ${SC_VERSION_HEADER}.${tmpsuffix} ${header_string})
+execute_process(COMMAND ${CMAKE_COMMAND} -E copy_if_different ${SC_VERSION_HEADER}.${tmpsuffix} ${SC_VERSION_HEADER})
+execute_process(COMMAND ${CMAKE_COMMAND} -E remove ${SC_VERSION_HEADER}.${tmpsuffix})

 if(NOT SC_IS_SUBBUILD)
  message("-- sc_version_string.h is up-to-date.")
Author	SHA1	Message	Date
Jeff Epler	d39fbaf4d7	sc_version_string: Use temporary names resilient against parallel builds In #359 I identify a race condition between multiple parallel invocations of cmake, which can arise naturally during ctests. Now that the file contents will not change without an intervening git commit, it is sufficient to ensure that the parallel invocations use distinct temporary file names with high probability.	2017-08-21 08:31:05 -05:00
Jeff Epler	e422262877	sc_version_string: omit the date and time when testing As analyzed in #359, if the header contains the current time, it will be updated while running the testsuite; this, in turn, causes multiple cmake processes to attempt to update targets like lib/libexpress.so.2.0.0 at the same time, causing test failures.	2017-08-21 08:31:00 -05:00
Mark	71fe947ff5	Merge pull request #361 from jepler/appveyor-single-thread-test appveyor build: don't use ctest parallelism	2017-08-19 17:12:28 -04:00
Mark	beb2a595f1	Merge pull request #357 from jepler/nullptr-bool Fix build error with g++ 6.3 (Debian Stretch)	2017-08-19 15:41:33 -04:00
Jeff Epler	0fbc3c0c84	Fix build error with g++ 6.3 (Debian Stretch) On this platform, TEST_NULLPTR fails, even though nullptr and nullptr_t are supported: /home/jepler/src/stepcode/build/CMakeFiles/CMakeTmp/src.cxx:4:23: error: converting to 'bool' from 'std::nullptr_t' requires direct-initialization [-fpermissive] int main() {return !!f();} ~^~ Subsequent to this failure, the workaround definitions in sc_nullptr.h prevent standard C++ headers (which must refer to real nullptr) to fail. The failure occurs because the C++ standard apparently does not state that operator! may be used on nullptr. Despite this, some compilers have historically allowed it. g++ 6.3's behavior appears to be aligned with the standard. As requested by @brlcad, ensure that the function 'f' is used from main, to avoid a clever (but not nullptr-supporting) compiler from somehow skipping 'f' altogether, creating a false positive for nullptr support.	2017-08-15 06:50:56 -05:00