$gcc problemMatcher only ever shows the first error or warning

I have a Visual Studio Code C project based on CMake, compiled using gcc. I've created a custom task for building the project, and have specified $gcc for its problemMatcher property.

However, when I build and there are compile errors, it only ever lists the first error returned, rather than all of them. How do I fix this?

Here is my tasks.json:

{"version": "2.0.0","tasks": [        {"type": "cmake","label": "CMake: build application","command": "build","presentation": {"echo": false,"reveal": "always","focus": false,"close": false,"panel": "dedicated","revealProblems": "onProblem","showReuseMessage": false,"clear": true            },"targets": ["all"            ],"group": {"kind": "build","isDefault": true            },"detail": "CMake build task","problemMatcher": ["$gcc"]        }    ]}