This meta-bug tracks those bugs specifically related to C99 conformance. The corresponding bug for C90 is bug 16620. Most C99 status is not tracked here but in <http://gcc.gnu.org/c99status.html>. Only issues with specific open bug reports are tracked here. My roadmap giving one possible sequence for the implementation of C99 features is <http://www.srcf.ucam.org/~jsm28/gcc/#stdc>, but the partial ordering constraints between different features are pretty weak.
Strongly target-specific bugs that might be considered conformance issues but are not shown as dependencies because of their target-specific nature include: bug 323 (the C parts, fixed on c-4_5-branch), bug 545, bug 26374, bug 37845. Bug 30484 should probably not be considered a conformance bug given WG14 discussions.