Commands implicitly threaded in Makefiles ?

Question

Hi,

I have a "super" makefile which launches two "sub" make file:

libwebcam: @echo -e "\nInvoking libwebcam make." $(MAKE) -C $(TOPDIR)/libwebcam

uvcdynctrl: @echo -e "\nInvoking uvcdynctrl make." $(MAKE) -C $(TOPDIR)/uvcdynctrl

uvcdynctrl uses libwebcam... I noticed that those two builds are launched as separate threads by make ! Thus sometimes the lib is not available when uvcdynctrl starts being built, and I get errors. By default, make should not launch commands as threads since this is available only through -j (number of jobs) and, according to the make manual, there is no thread by default. I run this on an Ubuntu.

Did someone face the same issue ?

Apple92

Answer 1

They should not be built concurrently unless you specify a -j argument to make at your top-level invocation. If you are doing so, then you need to set up dependencies properly to note that uvcdynctrl depends on libwebcam.

Answer 2

I don't know why you're commands are being threaded, but threading is not the problem, dependency is. If you set up the dependency correctly this error won't appear and if you don't it may appear, threads or no threads.

In the uvcdynctrl makefile, make libwebcam a prerequisite of uvcdynctrl and put in the rule for making libwebcam.