I'm not sure what changed in my system, because about two months ago, I built the C driver from source without problems.

But after a pull and/or a fresh clone of the master branch, and several versions checked out, using cmake build, I get the following error:

libmongoc-1.0.so.1.7.0-dev: undefined reference to `assert'
collect2: error: ld returned 1 exit status

There were some files with the following warning:

warning: implicit declaration of function ‘assert’ [-Wimplicit-function-declaration]

Solution, if this is really an issue, is to include <assert.h> in the affected files. This commit in facts shows the diff that works for me.

Btw, I'm building libbson from source as well.

Best