diff options
Diffstat (limited to 'src/compiler/analyzer.zc')
| -rw-r--r-- | src/compiler/analyzer.zc | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/src/compiler/analyzer.zc b/src/compiler/analyzer.zc index 839c1ef..55a96bb 100644 --- a/src/compiler/analyzer.zc +++ b/src/compiler/analyzer.zc @@ -1644,6 +1644,7 @@ int assigncheck(int k, int i, int rc) { // the function has no .u (its callers compiled after this point see it). an m // object is lent, not given, so returning it is an error, and so is a plain word // from an owned function that was called before its body. +int ret_borrowed; int retcheck(int c) { int i; if (isptr(xty) || xty == tword) { @@ -1670,9 +1671,16 @@ int retcheck(int c) { if ((isptr(xty) || isagg(xty)) && ((xaf && xaf[2] == 4) || (xbor >= 0 && lafact[xbor] && lafact[xbor][2] == 4))) { cerr("an array literal cannot escape its function through return"); return 0; } i = -1; if (c >= C_VAR && tracked(c - C_VAR)) i = c - C_VAR; + // a value that comes from a parameter the caller still owns (not a .d one, + // which is tracked) is a borrow: it can't become the caller's owned result. + if (c != C_FRESH && i < 0 && isptr(xty) && effect_mask(c)) { + if (fret) { cerr("a borrowed parameter cannot be returned as an owned result"); return 0; } + ret_borrowed = 1; + } if (i >= 0 && lstate[lroot(i)] == S_DEAD) { cerrn(i, "used after it was given away"); return 0; } if (i >= 0 && (lstate[i] == S_D || (lstate[i] == S_M && lown[i])) && (fret || finfer)) lstate[i] = S_U; // returning an owned object (a d object, or a local that owns one) gives it up, as u*x does if (!fret && finfer && (c == C_FRESH || (i >= 0 && lstate[i] == S_U))) { + if (ret_borrowed) cerr("this function also returns a borrowed parameter, so its result can't be owned"); if (sflag[finsym] & F_EARLY) serrn(sname[finsym], "is called before its body, so its owned return can't be known there; declare the return type with .u"); ssig[finsym] = ssig[finsym] | 1; // the return is owned: callers read it from the signature sflag[finsym] = sflag[finsym] | F_RETOWN; |