Fix global struct array init and runtime access

This commit addresses two critical issues with global struct arrays:
1. Global struct arrays were missing the is_global flag, causing them to
   be treated as local variables during code generation. This led to
   segmentation faults when accessing them at runtime since they were
   incorrectly loaded from the stack pointer (sp) instead of the global
   pointer (gp).
2. Global struct array initialization values were being parsed but
   ignored. The parser was only consuming the tokens without generating
   the necessary OP_load_constant instructions to initialize the values
   at runtime.

This fixes the test case where `struct point gpts1[] = { {3, 4} }` would
return 0 instead of the expected 7 when accessing gpts1[0].x+gpts1[0].y.

Author: jserv

src/parser.c

@@ -738,18 +738,43 @@ void parse_array_init(var_t *var,
                             var_t *field_val_raw = NULL;
 
                             if (parent == GLOBAL_BLOCK) {
-                                /* Global scope: only accept constants */
-                                if (lex_peek(T_numeric, NULL)) {
-                                    lex_accept(T_numeric);
-                                    /* Skip the value - we can't initialize at
-                                     * global scope yet */
-                                } else if (lex_peek(T_minus, NULL)) {
-                                    lex_accept(T_minus);
-                                    lex_accept(T_numeric);
+                                /* Global scope: accept constants and emit loads
+                                 * if emit_code is true */
+                                if (lex_peek(T_numeric, NULL) ||
+                                    lex_peek(T_minus, NULL)) {
+                                    int is_neg = 0;
+                                    if (lex_accept(T_minus))
+                                        is_neg = 1;
+                                    char numtok[MAX_ID_LEN];
+                                    lex_ident(T_numeric, numtok);
+                                    int num_val = read_numeric_constant(numtok);
+                                    if (is_neg)
+                                        num_val = -num_val;
+
+                                    if (emit_code) {
+                                        field_val_raw = require_var(parent);
+                                        gen_name_to(field_val_raw->var_name);
+                                        field_val_raw->init_val = num_val;
+                                        add_insn(parent, *bb, OP_load_constant,
+                                                 field_val_raw, NULL, NULL, 0,
+                                                 NULL);
+                                    }
+                                } else if (lex_peek(T_char, NULL)) {
+                                    char chtok[5];
+                                    lex_ident(T_char, chtok);
+
+                                    if (emit_code) {
+                                        field_val_raw =
+                                            require_typed_var(parent, TY_char);
+                                        gen_name_to(field_val_raw->var_name);
+                                        field_val_raw->init_val = chtok[0];
+                                        add_insn(parent, *bb, OP_load_constant,
+                                                 field_val_raw, NULL, NULL, 0,
+                                                 NULL);
+                                    }
                                 } else if (lex_peek(T_string, NULL)) {
                                     lex_accept(T_string);
-                                } else if (lex_peek(T_char, NULL)) {
-                                    lex_accept(T_char);
+                                    /* Strings not supported in struct fields */
                                 } else {
                                     error(
                                         "Global array initialization requires "
@@ -3996,6 +4021,7 @@ void read_global_statement(void)
 
             /* one or more declarators */
             var_t *var = require_typed_var(block, decl_type);
+            var->is_global = true; /* Global struct variable */
             read_partial_var_decl(var, NULL);
             add_insn(block, GLOBAL_FUNC->bbs, OP_allocat, var, NULL, NULL, 0,
                      NULL);