How to see the commands that are run by GNU make

gnu-makenvidia

I'm trying to debug a complex Makefile. How do you get GNU make to print all the commands it runs? I couldn't find the answer in the man page (using the -d flag doesn't seem to print it).

(This isn't necessary information to answer my question, but in case you're wondering: I'm having trouble compiling a project built on NVIDIA's CUDA library. I can compile it myself, but using their Makefile results in a nasty compiler error. I'd like to use their provided Makefile for easier packaging, and inclusion of other packages that they link in already.)

Best Answer

-n triggers a "dry run" in which no command is executed, though the commands which would execute are printed.

If your Makefile is recursive, though, this won't help much.

Lazy Set

VARIABLE = value

Normal setting of a variable, but any other variables mentioned with the value field are recursively expanded with their value at the point at which the variable is used, not the one it had when it was declared

Immediate Set

VARIABLE := value

Setting of a variable with simple expansion of the values inside - values within it are expanded at declaration time.

Lazy Set If Absent

VARIABLE ?= value

Setting of a variable only if it doesn't have a value. value is always evaluated when VARIABLE is accessed. It is equivalent to

ifeq ($(origin VARIABLE), undefined)
  VARIABLE = value
endif

See the documentation for more details.

Append

VARIABLE += value

Appending the supplied value to the existing value (or setting to that value if the variable didn't exist)

Difference between CPPFLAGS and CXXFLAGS in GNU Make

CPPFLAGS is supposed to be for flags for the C PreProcessor; CXXFLAGS is for flags for the C++ compiler.

The default rules in make (on my machine, at any rate) pass CPPFLAGS to just about everything, CFLAGS is only passed when compiling and linking C, and CXXFLAGS is only passed when compiling and linking C++.

Best Answer

Related Solutions

The difference between the GNU Makefile variable assignments =, ?=, := and +=

Lazy Set

Immediate Set

Lazy Set If Absent

Append

Difference between CPPFLAGS and CXXFLAGS in GNU Make

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