Race condition in Makefile ?

[XavierRaynaud]

From time to time, when compiling with "make -j", we have a race condition in Makefile, with messages like:

Fatal error: can't create al/src/th_al.o: No such file or directory

It seems the following patch solves the issue:

diff --git a/mith/Makefile b/mith/Makefile
index faeaea1..71a6f9d 100644
--- a/mith/Makefile
+++ b/mith/Makefile
@@ -54,4 +54,4 @@ print-%:
        @echo $* = $($*)  
        @echo [Defined at $(origin $*)] 
 
-$(TH_OBJS) : $(TH_HDRS)        
\ No newline at end of file
+$(TH_OBJS) : $(TH_HDRS)        $(MYDIRS)

[petertorelli]

@XavierRaynaud,
Very interesting, thanks for filing. I'd prefer to root out the problem rather than add a delay: adding a variable is not always the best way to solve a race. Let's understand the root cause in the build logic. However, since make is also used as the runner as well as the compilation manager, and since the code isn't particularly large, I'd rather just advise against using make -j. -Peter

[XavierRaynaud]

$(TH_OBJS) contains "al/src/th_al.o"
$(MYDIRS) contains "al/src/"
"al/src/th_al.o" requires "al/src/" dir to be created (otherwise, it fails with given error above)

One thing is sure: the creation of $(MYDIRS) is not performed in the right place in the Makefile.

[petertorelli]

Hmm. al/src isn't created, it is part of the repo. I'll keep an eye on this. If you can cause a failure repeatedly, that would help, but races are always hard to reproduce.