Can someone tell me what I'm doing wrong?

Clang Frontend
1

I'm trying to understand how to make a compile database. I can't switch to
cmake because my very large project uses gmake. So I've made a python
program to create a compile_commands.json file. It seems to have the right
information. For one file, named "x/y.cpp", when I cut the "command" value
out of the compile_commands.json file for "x/y.cpp" and execute it in a shell,
the command executes as I expect it to. However, when I try to run
"clang-check"
I get various odd errors. Here's the complete situation:

1.) The compile_commands.json file is in /a/b/c/compile_commands.json. I
    Think that makes "/a/b/c" the build directory in clang Tooling terms.
2.) The source file is in /a/b/c/x/y.cpp.
3.) The entry in compile_comands.json is:
        {"directory": "/a/b/c", "command": "clang++ x/y.cpp ... stuff
...", "file": "/a/b/c/x/y.cpp"}
    And of course there are many entries. This is just one of hundreds.

When I run clang-check, as the documentation seems to imply, using -p to name
the build directory, I get this:

% cd /a/b/c
% clang-check -p . x/y.cpp
Processing: /a/b/c/x/y.cpp.
error: no input files
error: unable to handle compilation, expected exactly one compiler job in ''
Error while processing /a/b/c/x/y.cpp.

Note: I get the same behavior putting the full path name for ".", when eliminate
      the "-p build_dir" completely. I also get the same behavior
when I cd into
      x and run the experiments (with y.cpp in place of x/y.cpp, of course).

Why am I being so dense about this? What am I missing? This seems very
unintuitive. I'm trying to build a tool which extracts dependence
information, but
I'm stymied right at the beginning.

2

I’m trying to understand how to make a compile database. I can’t switch to
cmake because my very large project uses gmake. So I’ve made a python
program to create a compile_commands.json file. It seems to have the right
information. For one file, named “x/y.cpp”, when I cut the “command” value
out of the compile_commands.json file for “x/y.cpp” and execute it in a shell,
the command executes as I expect it to. However, when I try to run
“clang-check”
I get various odd errors. Here’s the complete situation:

1.) The compile_commands.json file is in /a/b/c/compile_commands.json. I
Think that makes “/a/b/c” the build directory in clang Tooling terms.
2.) The source file is in /a/b/c/x/y.cpp.
3.) The entry in compile_comands.json is:
{“directory”: “/a/b/c”, “command”: “clang++ x/y.cpp … stuff
…”, “file”: “/a/b/c/x/y.cpp”}
And of course there are many entries. This is just one of hundreds.

Do you separate them with commas and put brackets around the whole construct? I.e., does your file look like this:

[

{“directory”: “/a/b/c/x”, “command”: "clang++ x/y.cpp … ", “file”: “/a/b/c/x/y.cpp”},

{“directory”: “/a/b/c/x”, “command”: "clang++ x/z.cpp … ", “file”: “/a/b/c/x/z.cpp”}

]

?