From 393cd7f8076692836c20c8f2723228ec8738c06c Mon Sep 17 00:00:00 2001
From: Alexey Andreev <konsoletyper@gmail.com>
Date: Mon, 19 Feb 2024 20:35:21 +0100
Subject: [PATCH] c: don't generate while(condition) loops due to UB in C spec

See https://www.iso-9899.info/n1570.html#6.8.5p6

Fix #885
---
 .../backend/c/generate/CodeGenerationVisitor.java      | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java b/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java
index aacb58a46..d8d34e7e8 100644
--- a/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java
+++ b/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java
@@ -1245,13 +1245,15 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
 
         int statementId = registerIdentifiedStatement(statement);
 
-        writer.print("while (");
+        writer.println("while (1) {").indent();
+
+        // This can't be moved to 'while', since C11 standard allows removing infinite loops
+        // See https://www.iso-9899.info/n1570.html#6.8.5p6
         if (statement.getCondition() != null) {
+            writer.print("if (!");
             statement.getCondition().acceptVisitor(this);
-        } else {
-            writer.print("1");
+            writer.println(") break;");
         }
-        writer.println(") {").indent();
 
         boolean oldEnd = end;
         for (Statement part : statement.getBody()) {