Hi. I tried to compare build.log from running mock with the output from directly running rpmbuild. rpmbuild: checking how to run the C preprocessor... gcc -E checking for an ANSI C-conforming const... yes checking for inline... inline build.log: checking how to run the C preprocessor... yes checking for an ANSI C-conforming const... gcc -E yes checking for inline... checking for grep that handles long lines and -e... /usr/bin/grep checking for egrep... /usr/bin/grep -E checking for ANSI C header files... inline It looks like mock is forcibly redirecting stdout and stderr through two different pipes and a race condition happens. The problem is the same as in many IDEs. Please, please, make this redirection optional. -- packaging mailing list packaging@xxxxxxxxxxxxxxxxxxxxxxx https://lists.fedoraproject.org/admin/lists/packaging@xxxxxxxxxxxxxxxxxxxxxxx