>From 3d3a9b173cf11a832a95e581dbfddb2da092b08a Mon Sep 17 00:00:00 2001
From: "Arnold D. Robbins" <address@hidden>
Date: Wed, 7 Sep 2016 06:42:22 +0300
Subject: [PATCH] Add duplicate case value checking to switch statements.

---
 tccgen.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)

diff --git a/tccgen.c b/tccgen.c
index 9ebd80a..6b4c682 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -4876,6 +4876,99 @@ static void label_or_decl(int l)
     decl(l);
 }
 
+struct case_label {
+    int value;
+    struct case_label *next;
+    size_t line;
+};
+
+struct switch_list {
+    struct switch_list *outer;
+    struct case_label *labels;
+    size_t num_labels;
+} *switch_list = NULL;
+
+static int label_compare(const void *l, const void *r)
+{
+    struct case_label **left = (struct case_label **) l;
+    struct case_label **right = (struct case_label **) r;
+    int ret;
+
+    ret = ((*left)->value - (*right)->value);
+    if (ret != 0)
+        return ret;
+
+    return ((*left)->line - (*right)->line);
+}
+
+static void switch_start()
+{
+    struct switch_list *nsw = tcc_malloc(sizeof(struct switch_list));
+    memset(nsw, 0, sizeof(*nsw));
+
+    if (switch_list != NULL)
+        nsw->outer = switch_list;
+
+    switch_list = nsw;
+}
+
+static void switch_end()
+{
+    struct case_label **labels = tcc_malloc(switch_list->num_labels * sizeof(struct case_label *));
+    int i;
+    struct case_label *l = switch_list->labels;
+    struct case_label *l2;
+    struct switch_list *outer = switch_list->outer;
+    static int have_dups = 0;
+
+    for (i = 0; i < switch_list->num_labels; i++) {
+        labels[i] = l;
+        l = l->next;
+    }
+
+    qsort(labels, switch_list->num_labels, sizeof(struct case_label *), label_compare);
+
+    for (i = 1; i < switch_list->num_labels; i++) {
+        if (labels[i-1]->value == labels[i]->value) {
+            have_dups = 1;
+            tcc_error_noabort("duplicate case label %d: lines %d and %d",
+                    labels[i]->value,
+                    labels[i-1]->line,
+                    labels[i]->line);
+        }
+    }
+
+    /* release all the memory */
+    tcc_free(labels);
+
+    for (l = switch_list->labels; l != NULL; l = l2) {
+        l2 = l->next;
+        tcc_free(l);
+    }
+
+    tcc_free(switch_list);
+    switch_list = outer;
+
+    if (have_dups && outer == NULL)
+        exit(1);
+}
+
+static void switch_add_case(int case_val)
+{
+    struct case_label *label = tcc_malloc(sizeof(struct case_label));
+
+    memset(label, 0, sizeof(*label));
+    label->value = case_val;
+    label->line = file->line_num;
+
+    if (switch_list) {
+        label->next = switch_list->labels;
+        switch_list->labels = label;
+        switch_list->num_labels++;
+    } else
+        tcc_free(label);
+}
+
 static void block(int *bsym, int *csym, int *case_sym, int *def_sym, 
                   int case_reg, int is_expr)
 {
@@ -5152,7 +5245,9 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
         a = 0;
         b = gjmp(0); /* jump to first case */
         c = 0;
+        switch_start();
         block(&a, csym, &b, &c, case_reg, 0);
+        switch_end();
         /* if no default, jmp after switch */
         if (c == 0)
             c = ind;
@@ -5167,10 +5262,12 @@ static void block(int *bsym, int *csym, int *case_sym, int *def_sym,
             expect("switch");
         next();
         v1 = expr_const();
+        switch_add_case(v1);
         v2 = v1;
         if (gnu_ext && tok == TOK_DOTS) {
             next();
             v2 = expr_const();
+            switch_add_case(v2);
             if (v2 < v1)
                 tcc_warning("empty case range");
         }
-- 
2.7.4