How do I force make/GCC to show me the commands?

gcc makefile verbosity

I'm trying to debug a compilation problem, but I cannot seem to get GCC (or maybe it is make??) to show me the actual compiler and linker commands it is executing.

Here is the output I am seeing:

  CCLD   libvirt_parthelper
libvirt_parthelper-parthelper.o: In function `main':
/root/qemu-build/libvirt-0.9.0/src/storage/parthelper.c:102: undefined reference to `ped_device_get'
/root/qemu-build/libvirt-0.9.0/src/storage/parthelper.c:116: undefined reference to `ped_disk_new'
/root/qemu-build/libvirt-0.9.0/src/storage/parthelper.c:122: undefined reference to `ped_disk_next_partition'
/root/qemu-build/libvirt-0.9.0/src/storage/parthelper.c:172: undefined reference to `ped_disk_next_partition'
/root/qemu-build/libvirt-0.9.0/src/storage/parthelper.c:172: undefined reference to `ped_disk_next_partition'
collect2: ld returned 1 exit status
make[3]: *** [libvirt_parthelper] Error 1

What I want to see should be similar to this:

$ make
gcc -Wall   -c -o main.o main.c
gcc -Wall   -c -o hello_fn.o hello_fn.c
gcc   main.o hello_fn.o   -o main

Notice how this example has the complete gcc command displayed. The above example merely shows things like "CCLD libvirt_parthelper". I'm not sure how to control this behavior.

Are you running a makefile, or just a gcc command?

This looks like Kbuild or Autotools output. Try make V=1.

Related: the opposite question Control the output of a make command to be less verbose, don't echo each command

Zombo

To invoke a dry run:

make -n

This will show what make is attempting to do.

Found it :) make V=1 Although the above suggestion of "make -n" worked as well. :) Thank you all for your responses.

Difference is that make -n does not execute the commands. Thus correct answer is make V=1

make V=1 is only working if the Makefile supports it. automake's makefiles do that, but many others don't.

For CMake, use make VERBOSE=1; for GNU autotools make V=1.

@m-ric if you want to run actually run the commands, consider make SHELL='sh -x': stackoverflow.com/a/32010960/895245

Peter Mortensen

Library makefiles, which are generated by autotools (the ./configure you have to issue) often have a verbose option, so basically, using make VERBOSE=1 or make V=1 should give you the full commands.

But this depends on how the makefile was generated.

The -d option might help, but it will give you an extremely long output.

Note: CMake-generated Makefiles only support VERBOSE=1, not V=1.

V=1 worked for me, compiling nuttx with mips-linux-gnu-gcc, thank you.

Ciro Santilli Путлер Капут 六四事

Build system independent method

make SHELL='sh -x'

is another option. Sample Makefile:

a:
    @echo a

Output:

+ echo a
a

This sets the special SHELL variable for make, and -x tells sh to print the expanded line before executing it.

One advantage over -n is that is actually runs the commands. I have found that for some projects (e.g. Linux kernel) that -n may stop running much earlier than usual probably because of dependency problems.

One downside of this method is that you have to ensure that the shell that will be used is sh, which is the default one used by Make as they are POSIX, but could be changed with the SHELL make variable.

Doing sh -v would be cool as well, but Dash 0.5.7 (Ubuntu 14.04 sh) ignores for -c commands (which seems to be how make uses it) so it doesn't do anything.

make -p will also interest you, which prints the values of set variables.

CMake generated Makefiles always support VERBOSE=1

As in:

mkdir build
cd build
cmake ..
make VERBOSE=1

Dedicated question at: Using CMake with GNU Make: How can I see the exact commands?

Definitely the best answer which doesn't depend on how well the original Makefile was written/generated

If anyone can explain the downvote, let me know so I can learn and improve the information ;-)

make SHELL='$$SHELL -x' will make $SHELL literal which is not evaluated. Using make SHELL="$SHELL -x" will work.

this is the best generic answer, in contrast to some other answers this does not depend on using cmake

make SHELL='sh -x' is super!

Flow

Since GNU Make version 4.0, the --trace argument is a nice way to tell what and why a makefile do, outputing lines like:

makefile:8: target 'foo.o' does not exist

makefile:12: update target 'foo' due to: bar

This argument prints more detailed information than dry run. It is very helpful to understand make systems which has complex build process like dpdk.

@makerj: Perhaps, but it does actually execute the commands, unlike make -n.

TarmoPikaro

Use make V=1

Other suggestions here:

make VERBOSE=1 - did not work at least from my trials.

make -n - displays only logical operation, not command line being executed. E.g. CC source.cpp

make --debug=j - works as well, but might also enable multi threaded building, causing extra output.

make VERBOSE=1 is for CMake. Your trials were most likely with GNU autotools-based projects.

Santiago Villafuerte

I like to use:

make --debug=j

https://linux.die.net/man/1/make

--debug[=FLAGS]

Print debugging information in addition to normal processing. If the FLAGS are omitted, then the behavior is the same as if -d was specified. FLAGS may be a for all debugging output (same as using -d), b for basic debugging, v for more verbose basic debugging, i for showing implicit rules, j for details on invocation of commands, and m for debugging while remaking makefiles.

It doesn't necessarily show the command it executes. You may just get Reaping winning child xyz and Jobserver client (fds 3,4) and Need a job token; we don't have children and so on.

Agreed, @einpoklum.

Peter Mortensen

Depending on your automake version, you can also use this:

make AM_DEFAULT_VERBOSITY=1

Reference: AM_DEFAULT_VERBOSITY

Note: I added this answer since V=1 did not work for me.

This is only if you use GNU autotools / automake.

@einpoklum The answer states this...

How do I force make/GCC to show me the commands?

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