The following issue has been SUBMITTED. ====================================================================== https://cmake.org/Bug/view.php?id=15976 ====================================================================== Reported By: Cristian Rodríguez Assigned To: ====================================================================== Project: CMake Issue ID: 15976 Category: CMake Reproducibility: always Severity: minor Priority: normal Status: new ====================================================================== Date Submitted: 2016-02-16 20:26 EST Last Modified: 2016-02-16 20:26 EST ====================================================================== Summary: cmSystemTools::RandomSeed() requests excessive entropy per invocation Description: cmSystemTools::RandomSeed() opens a *buffered* ifstream, the final result is that each invocation requests _IO_BUFSIZ -1 of entropy to the operating system instead of just sizeof(seed)
Steps to Reproduce: mkdir test_cmake echo "PROJECT(foo)" > CMakeLists.txt cd test_cmake strace -f -ocmake.trace cmake . open cmake.trace 10768 26289 open("/dev/urandom", O_RDONLY) = 4 10769 26289 read(4, "h\304j\vx\314\26\0042\250g\275\0014,\256\251\257T&\304\212\310\347q\201\263\324\330\273z8"..., 8191) = 8191 10770 26289 close(4) = 0 10771 26289 write(3, "cmake_minimum_required(VERSION 3"..., 795) = 795 10772 26289 close(3) = 0 10773 26289 stat("/home/crrodriguez/test_cmake/CMakeFiles/CMakeTmp", {st_mode=S_IFDIR|0755, st_size=58, ...}) = 0 10774 26289 getcwd("/home/crrodriguez/test_cmake", 2048) = 29 Additional Information: git diff diff --git a/Source/cmSystemTools.cxx b/Source/cmSystemTools.cxx index 3ba7287..26bec34 100644 --- a/Source/cmSystemTools.cxx +++ b/Source/cmSystemTools.cxx @@ -2184,8 +2184,10 @@ unsigned int cmSystemTools::RandomSeed() } seed; // Try using a real random source. - cmsys::ifstream fin("/dev/urandom"); - if(fin && fin.read(seed.bytes, sizeof(seed)) && + cmsys::ifstream fin; + fin.rdbuf()->pubsetbuf(0, 0); + fin.open("/dev/urandom"); + if(fin.good() && fin.read(seed.bytes, sizeof(seed)) && fin.gcount() == sizeof(seed)) { return seed.integer; ====================================================================== Issue History Date Modified Username Field Change ====================================================================== 2016-02-16 20:26 Cristian RodríguezNew Issue ====================================================================== -- Powered by www.kitware.com Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ Kitware offers various services to support the CMake community. For more information on each offering, please visit: CMake Support: http://cmake.org/cmake/help/support.html CMake Consulting: http://cmake.org/cmake/help/consulting.html CMake Training Courses: http://cmake.org/cmake/help/training.html Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Follow this link to subscribe/unsubscribe: http://public.kitware.com/mailman/listinfo/cmake-developers