throw somed attributes on a few functions

include/notcurses/notcurses.h

@@ -554,6 +554,7 @@ cell_init(cell* c){
 // Breaks the UTF-8 string in 'gcluster' down, setting up the cell 'c'. Returns
 // the number of bytes copied out of 'gcluster', or -1 on failure. The styling
 // of the cell is left untouched, but any resources are released.
+__attribute__ ((nonnull (1, 2, 3)))
 API int cell_load(struct ncplane* n, cell* c, const char* gcluster);
 
 // cell_load(), plus blast the styling with 'attr' and 'channels'.

src/lib/egcpool.h

@@ -110,7 +110,7 @@ egcpool_alloc_justified(const egcpool* pool, int len){
 // should not be less than 2 bytes (such a cluster should be directly stored in
 // the cell). returns -1 on error, and otherwise a non-negative offset. 'ulen'
 // must be the number of bytes to lift from egc (utf8_egc_len()).
-static inline int
+__attribute__ ((nonnull (1, 2))) static inline int
 egcpool_stash(egcpool* pool, const char* egc, size_t ulen){
   int len = ulen + 1; // count the NUL terminator
   if(len <= 2){ // should never be empty, nor a single byte + NUL
@@ -236,8 +236,8 @@ egcpool_dump(egcpool* pool){
   pool->poolused = 0;
 }
 
-static inline const char*
-egcpool_extended_gcluster(const egcpool* pool, const cell* c){
+__attribute__ ((__returns_nonnull__)) static inline const char*
+egcpool_extended_gcluster(const egcpool* pool, const cell* c) {
   uint32_t idx = cell_egc_idx(c);
   return pool->pool + idx;
 }

src/lib/internal.h

@@ -599,8 +599,9 @@ cell_duplicate_far(egcpool* tpool, cell* targ, const ncplane* splane, const cell
     targ->gcluster = c->gcluster;
     return !!c->gcluster;
   }
-  size_t ulen = strlen(extended_gcluster(splane, c));
-  int eoffset = egcpool_stash(tpool, extended_gcluster(splane, c), ulen);
+  const char* egc = extended_gcluster(splane, c);
+  size_t ulen = strlen(egc);
+  int eoffset = egcpool_stash(tpool, egc, ulen);
   if(eoffset < 0){
     return -1;
   }

src/lib/render.c

@@ -374,6 +374,7 @@ fprintf(stderr, "WROTE %u [%s] to %d/%d (%d/%d)\n", targc->gcluster, extended_gc
   return 0;
 }
 
+// it's not a pure memset(), because CELL_ALPHA_OPAQUE is the zero value
 static void
 init_fb(cell* fb, int dimy, int dimx){
   for(int y = 0 ; y < dimy ; ++y){