Using static analyzer included in clang 3.6.2:
$ ./autogen.sh 
$ ./configure
$ scan-build make
  CC       src/libtess/dict.lo
  CC       src/libtess/geom.lo
  CC       src/libtess/memalloc.lo
  CC       src/libtess/mesh.lo
  CC       src/libtess/normal.lo
src/libtess/normal.c:112:6: warning: Assigned value is garbage or undefined
  v1 = minVert[i];
     ^ ~~~~~~~~~~
src/libtess/normal.c:113:6: warning: Assigned value is garbage or undefined
  v2 = maxVert[i];
     ^ ~~~~~~~~~~
2 warnings generated.
  CC       src/libtess/priorityq.lo
  CC       src/libtess/render.lo
  CC       src/libtess/sweep.lo
src/libtess/sweep.c:779:11: warning: Use of memory after it is freed
    if( ! regUp->dirty ) {
          ^~~~~~~~~~~~
src/libtess/sweep.c:803:10: warning: Use of memory after it is freed
          eLo = regLo->eUp;
                ^~~~~~~~~~
src/libtess/sweep.c:808:10: warning: Use of memory after it is freed
          eUp = regUp->eUp;
                ^~~~~~~~~~
3 warnings generated.