1378467 - Linux build failures on TreeHerder with "cc1plus: error: to generate dependencies you must specify either -M or -MM"

Status: RESOLVED DUPLICATE of bug 1376593

(Firefox Build System :: General, enhancement)

Description

[Daniel Holbert [:dholbert]]

Two people independently ran into this "build error" on TreeHerder recently:
> cc1plus: error: to generate dependencies you must specify either -M or -MM

In both cases:
 - This was the proximal error-ish line in the log before "*** [Unified_cpp_whatever.o] Error 1", which makes it look like the proximal build issue.
 - The "guilty" patch had anything to do with generating dependencies or command-line arguments. i.e. this error seems completely unrelated to the code changes that "cause" it.
 - So, this error seems like noise or some awkwardly-converted way of reporting the *actual* cause of the build error -- and it's very confusing to diagnose / act on.

Instance #1:
https://treeherder.mozilla.org/logviewer.html#?job_id=109671389&repo=try&lineNumber=9075

Instance #2:
https://treeherder.mozilla.org/logviewer.html#?job_id=112013077&repo=try&lineNumber=5899

glandium, I believe you mentioned in IRC that this sometimes has to do with build warnings treated as errors -- but those warnings/errors seem to be masked in the log, so there's no clear way to identify or act on them.

Do we know what's going on here? Can we fix things so that TreeHerder build errors can be more actionable?

Comment 1

[Nathan Froyd [:froydnj]]

I'm pretty sure this is a dup of bug 1376593.

Comment 2

[Daniel Holbert [:dholbert]]

Indeed, thanks! (I've updated the bug summary on that other bug, to make it more discoverable)