From e44f3a2ffc7ced5e75cca7657aaa60ef27da89aa Mon Sep 17 00:00:00 2001
From: Roberto I <roberto@inf.puc-rio.br>
Date: Sat, 8 Nov 2025 11:43:42 -0300
Subject: Global initialization checks name conflict

Initialization "global a = 10" raises an error if global 'a' is already
defined, that is, it has a non-nil value.
---
 lparser.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

(limited to 'lparser.c')

diff --git a/lparser.c b/lparser.c
index 40a30ff6..77141e79 100644
--- a/lparser.c
+++ b/lparser.c
@@ -1875,6 +1875,16 @@ static lu_byte getglobalattribute (LexState *ls, lu_byte df) {
 }
 
 
+static void checkglobal (LexState *ls, TString *varname, int line) {
+  FuncState *fs = ls->fs;
+  expdesc var;
+  int k;
+  buildglobal(ls, varname, &var);  /* create global variable in 'var' */
+  k = var.u.ind.keystr;  /* index of global name in 'k' */
+  luaK_codecheckglobal(fs, &var, k, line);
+}
+
+
 /*
 ** Recursively traverse list of globals to be initalized. When
 ** going, generate table description for the global. In the end,
@@ -1883,7 +1893,8 @@ static lu_byte getglobalattribute (LexState *ls, lu_byte df) {
 ** the stack to the corresponding table description. 'n' is the variable
 ** being handled, range [0, nvars - 1].
 */
-static void initglobal (LexState *ls, int nvars, int firstidx, int n) {
+static void initglobal (LexState *ls, int nvars, int firstidx, int n,
+                        int line) {
   if (n == nvars) {  /* traversed all variables? */
     expdesc e;
     int nexps = explist(ls, &e);  /* read list of expressions */
@@ -1895,8 +1906,9 @@ static void initglobal (LexState *ls, int nvars, int firstidx, int n) {
     TString *varname = getlocalvardesc(fs, firstidx + n)->vd.name;
     buildglobal(ls, varname, &var);  /* create global variable in 'var' */
     enterlevel(ls);  /* control recursion depth */
-    initglobal(ls, nvars, firstidx, n + 1);
+    initglobal(ls, nvars, firstidx, n + 1, line);
     leavelevel(ls);
+    checkglobal(ls, varname, line);
     storevartop(fs, &var);
   }
 }
@@ -1913,7 +1925,7 @@ static void globalnames (LexState *ls, lu_byte defkind) {
     nvars++;
   } while (testnext(ls, ','));
   if (testnext(ls, '='))  /* initialization? */
-    initglobal(ls, nvars, lastidx - nvars + 1, 0);
+    initglobal(ls, nvars, lastidx - nvars + 1, 0, ls->linenumber);
   fs->nactvar = cast_short(fs->nactvar + nvars);  /* activate declaration */
 }
 
@@ -1943,6 +1955,7 @@ static void globalfunc (LexState *ls, int line) {
   fs->nactvar++;  /* enter its scope */
   buildglobal(ls, fname, &var);
   body(ls, &b, 0, ls->linenumber);  /* compile and return closure in 'b' */
+  checkglobal(ls, fname, line);
   luaK_storevar(fs, &var, &b);
   luaK_fixline(fs, line);  /* definition "happens" in the first line */
 }
-- 
cgit v1.2.3-55-g6feb