"ninja: build stopped: subcommand failed." - which subcommand ? No clue in log.

[Jason Vas Dias]

Please, improve ninja to say WHAT subcommand failed ; simply exiting with
"ninja: build stopped: subcommand failed."
is useless - it doesn't tell people WHAT failed.

My log file, for a GCC build, shows NO error messages from GCC, so I'm stuck.

I have to run the whole build with 'strace -s8192 -f -e trace=execve' and tediously
analyse this log to find which sub-processes / commands have failed.

This is unacceptable - I'd recommend converting projects from ninja use to plain GNU Make
use or CMake use because of this issue (and many others).

[David Turner]

You may be misunderstood. Ninja already prints the subcommand which failed before this message (as well as the combined stdout + stderr of that command). You can verify that by writing the following to a build.ninja file the invoking Ninja in the same directory:

rule foo
  command = echo "to_stdout"; echo >&2 "to_stderr"; exit 1

build out: foo

You will get:

[1/1] echo "to_stdout"; echo >&2 "to_stderr"; exit 1
FAILED: out 
echo "to_stdout"; echo >&2 "to_stderr"; exit 1
to_stdout
to_stderr
ninja: build stopped: subcommand failed.

However, the failed command + its outputs are sent to stderr, while the "ninja: build stopped: subcommand failed" message is sent to stdout.

Did you redirect stderr to a different file before invoking Ninja? That would explain what you're are seeing.