Here's an encouraging graph from our regular Coverity scans of the curl source code, showing that we've maintained a fairly low "defect density" over the last two years, staying way below the average density level.
Click the image to view it slightly larger.
Defect density is simply the number of found problems per 1,000 lines of code. As a little (and probably unfair) comparison, right now when curl is flat on 0, Firefox is at 0.47, c-ares at 0.12 and libssh2 at 0.21.
Coverity is still the primary static code analyzer for C code that I'm aware of. None of the flaws Coverity picked up in curl during the last two years were detected by clang-analyzer for example.