analyzer: check borrow returns of forward-called functions at the unit's end; borrows clause for prototypes, definitions, externs and function types, checked against the body

1 files changed, 48 insertions, 0 deletions

diff --git a/src/compiler/analyzer.zc b/src/compiler/analyzer.zc
index 48debee..103f732 100644
--- a/src/compiler/analyzer.zc
+++ b/src/compiler/analyzer.zc
@@ -83,6 +83,51 @@ int effect_specialize(int original, int instance, word requirements, word edges)
 	while (e && e != edges) { if (e[3] == original) e[3] = instance; e = e[0]; }
 	return 0;
 }
+// borrow returns of functions called before their body. such a call's result
+// may turn out to alias an argument's owner, which is only known once the body
+// has been read. the result's local keeps a shadow record (callee, the mask of
+// parameters that got the owner, the owner, the token after the call, so only a call that is the whole right side counts); a
+// use of the local after its owner ended is remembered, and effect_finish
+// reports it when the callee's return aliases one of those parameters.
+word shadow_new(int callee, int mask, int owner) {
+ word e;
+ if (!fchk || !live || dry || owner < 0 || !mask) return 0;
+ e = talloc(4); e[0] = callee; e[1] = mask; e[2] = owner; e[3] = tpack();
+ return e;
+}
+// the local i is assigned: it takes the shadow of a forward call that is its whole right side.
+int shadow_take(int i) {
+ if (!local_shadow) return 0;
+ local_shadow[i] = 0;
+ // the local read just before is the target of this assignment, not a use
+ if (effect_shadows && effect_shadows[10] == i && effect_shadows[11] == lreadpos[i]) effect_shadows = effect_shadows[0];
+ if (xshadow && xshadow[3] == tpack()) local_shadow[i] = xshadow;
+ xshadow = 0; return 0;
+}
+int shadow_use(int i) {
+ word s = local_shadow[i], e; int o = s[2];
+ if (!fchk || !live || lstate[o] != S_DEAD) return 0;
+ local_shadow[i] = 0;
+ e = talloc(12); e[10] = i; e[11] = tpack(); e[0] = effect_shadows; e[1] = s[0]; e[2] = s[1]; e[3] = tpack(); e[4] = curinc; e[5] = effect_floor;
+ e[6] = lname[i]; e[7] = 0; if (local_end_info) e[7] = local_end_info[o]; e[8] = lname[o]; e[9] = local_ended[o];
+ effect_shadows = e; return 0;
+}
+int shadow_finish(int from) {
+ word e = effect_shadows, next; int flags, k;
+ effect_shadows = 0;
+ while (e) {
+  next = e[0];
+  if (e[5] < from) { e[0] = effect_shadows; effect_shadows = e; e = next; continue; }
+  flags = 0; k = 0;
+  while (k < 24) { if ((e[2] >> k) & 1) flags = flags | effect_get(e[1], k); k++; }
+  if ((flags & (EF_ALIAS | EF_IDENTITY)) && !(flags & EF_UNKNOWN) && !dry) {
+   tunpack(e[3]); curinc = e[4]; panic = 0;
+   errat(); ended_message(e[6], e[7], e[8], e[9]); rt.put_s("; "); rt.put_s(sname[e[1]]); rt.put_s(", defined after this call, returns a borrow of its argument"); errend();
+  }
+  e = next;
+ }
+ return 0;
+}
 int effect_finish(int from) {
  word e, r, next; int changed = 1, flags, prior, save = tpack(), inc = curinc, i = 0;
  if (chkabort) return 0;
@@ -110,6 +155,7 @@ int effect_finish(int from) {
   }
   e = next;
  }
+ shadow_finish(from);
  tunpack(save); curinc = inc; return 0;
 }
 int borrow_begin() { return 0; }
@@ -393,6 +439,7 @@ int newloc(int n) {
  if (!local_captured) local_captured = chk_resize(0, 0, loccap); local_captured[i] = 0;
  if (!local_ended) local_ended = chk_resize(0, 0, loccap); local_ended[i] = 0;
  if (!local_end_info) local_end_info = chk_resize(0, 0, loccap); local_end_info[i] = 0;
+ if (!local_shadow) local_shadow = chk_resize(0, 0, loccap); local_shadow[i] = 0;
 	lpos[i] = 0;
 	lreadpos[i] = 0;
 	lowner[i] = 0;
@@ -1459,6 +1506,7 @@ int reassign_free(int i, int rc, int bor) {
 // a store of class rc into an lvalue of kind k (local or container index i)
 int assigncheck(int k, int i, int rc) {
 	int st, j, r, js, bor, origin = effect_origin(rc);
+ if (k == LV_LOCAL) shadow_take(i); else xshadow = 0;
  if (k == LV_LOCAL && local_origin) { local_origin[i] = origin; local_origin_mask[i] = local_origin_mask[i] | effect_mask(rc); }
  if (k == LV_ELEM) { effect_note_mask(effect_mask(C_VAR + i), EF_WRITE); }
  if (k != LV_LOCAL && isptr(xty)) effect_note_mask(effect_mask(rc), EF_RETAIN);