do not blow up the stack with lots of varargs

3 files changed, 61 insertions, 17 deletions

diff --git a/src/analyzer.js b/src/analyzer.js
index 4aac53a8..6fd7ef66 100644
--- a/src/analyzer.js
+++ b/src/analyzer.js
@@ -788,26 +788,49 @@ function analyzer(data, sidePass) {
           delete item.allocatedSize;
         }
         func.initialStack = index;
-        // We need to note if stack allocations other than initial allocs can happen here
-        // (for example, via alloca). If so, we need to rewind the stack when we leave.
         func.otherStackAllocations = false;
-        var finishedInitial = false;
-        for (var i = 0; i < lines.length; i++) {
-          var item = lines[i].value;
-          if (!item || item.intertype != 'alloca') {
-            finishedInitial = true;
-            continue;
+        while (func.initialStack == 0) { // one-time loop with possible abort in the middle
+          // If there is no obvious need for stack management, perhaps we don't need it
+          // (we try to optimize that way with SKIP_STACK_IN_SMALL). However,
+          // we need to note if stack allocations other than initial allocs can happen here
+          // If so, we need to rewind the stack when we leave.
+
+          // By-value params are causes of additional allocas (although we could in theory make them normal allocas too)
+          func.params.forEach(function(param) {
+            if (param.byVal) {
+              func.otherStackAllocations = true;
+            }
+          });
+          if (func.otherStackAllocations) break;
+
+          // Allocas
+          var finishedInitial = false;
+          for (var i = 0; i < lines.length; i++) {
+            var item = lines[i].value;
+            if (!item || item.intertype != 'alloca') {
+              finishedInitial = true;
+              continue;
+            }
+            if (item.intertype == 'alloca' && finishedInitial) {
+              func.otherStackAllocations = true;
+              break;
+            }
           }
-          if (item.intertype == 'alloca' && finishedInitial) {
-            func.otherStackAllocations = true;
+          if (func.otherStackAllocations) break;
+
+          // Varargs
+          for (var i = 0; i < lines.length; i++) {
+            var item = lines[i];
+            if (item.value) item = item.value;
+            if (item.intertype == 'call' && isVarArgsFunctionType(item.type)) {
+              func.otherStackAllocations = true;
+              break;
+            }
           }
+          if (func.otherStackAllocations) break;
+
+          break;
         }
-        // by-value params are also causes of additional allocas (although we could in theory make them normal allocas too)
-        func.params.forEach(function(param) {
-          if (param.byVal) {
-            func.otherStackAllocations = true;
-          }
-        });
       });
       this.forwardItem(data, 'Relooper');
     }
diff --git a/src/runtime.js b/src/runtime.js
index 2b81258d..6439d0ed 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -34,7 +34,8 @@ var RuntimeGenerator = {
 
   stackEnter: function(initial, force) {
     if (initial === 0 && SKIP_STACK_IN_SMALL && !force) return '';
-    var ret = 'var __stackBase__  = STACKTOP; STACKTOP += ' + initial;
+    var ret = 'var __stackBase__  = STACKTOP';
+    if (initial > 0) ret += '; STACKTOP += ' + initial;
     if (USE_TYPED_ARRAYS == 2) {
       assert(initial % QUANTUM_SIZE == 0);
       if (ASSERTIONS) {
diff --git a/tests/runner.py b/tests/runner.py
index 18ce11af..dd11b950 100644
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -1459,6 +1459,26 @@ if 'benchmark' not in str(sys.argv) and 'sanity' not in str(sys.argv):
         '''
         self.do_run(src, 'sum:9780*')
 
+        # We should not blow up the stack with numerous varargs
+
+        src = r'''
+          #include <stdio.h>
+          #include <stdlib.h>
+
+          void func(int i) {
+            printf("%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,%d\n",
+                     i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i, i);
+          }
+          int main() {
+            for (int i = 0; i < 1024; i++)
+              func(i);
+            printf("ok!\n");
+            return 0;
+          }
+        '''
+        Settings.TOTAL_STACK = 1024
+        self.do_run(src, 'ok!')
+
     def test_array2(self):
         src = '''
           #include <stdio.h>