Using Clang's scan-build with scons and C++11

Question

I've added everything to my $PATH and I've tweaked my SConstruct to set the appropriate environment variables, as per these answers [ 1, 2, 3 ]. Now when I run

scan-build --use-c++=`which clang++` scons

the build begins, and I can see the process forked by scons is

/path/to/c++-analyzer ... -std=c++11 ...

The object file successfully builds, but then I get an error:

could not find clang line

This error occurs in c++-analyzer when the forked process does not contain the string -cc1. But if I check ps aux, I clearly see

/path/to/clang -cc1 ...

How could the program build properly but the static analyzer fail like this?

---

For reference, if I manually run

scan-build clang++ <parameters from scons>

then the build succeeds and the report is generated!

I can also "cheat" by adding

env["ENV"]["PATH"] = os.environ["PATH"]

and then running

CXX="scan-build clang++" scons

I just can't run scan-build on scons itself with an unmodified SConstruct.

Answer 1

The problem is that clang is not on the search path in the execution environment (Wayback Machine). This explains why adding the line env["ENV"]["PATH"] = os.environ["PATH"] solves the issue.

To run scan-build on an unmodified SConstruct you can put the clang executable (clang++ and possibly clang) on the search path used by the execution environment, e.g. by creating a symbolic link from /usr/bin/clang++ to your /path/to/clang++ on Linux.

Answer 2

I had the identical problem: the object file successfully builds, but then I got the error:

could not find clang line

The problem was that I was using a flag valid for gcc but invalid for clang.

touch empty.c

scan-build gcc -fdiagnostics-show-caret -c empty.c
scan-build: Using '/usr/bin/clang-8.exe' for static analysis
could not find clang line
...

scan-build --use-cc=clang gcc -fdiagnostics-show-caret -c empty.c
scan-build: Using '/usr/bin/clang-8.exe' for static analysis
clang-8: error: unknown argument: '-fdiagnostics-show-caret'
...

Removing the -fdiagnostics-show-caret makes the problem go away:

scan-build gcc -c empty.c
scan-build: Using '/usr/bin/clang-8.exe' for static analysis
...

Also, to muddy the waters, clang's name for this switch is -fcaret-diagnostics, which gcc will not accept.