From d1efe1af90813a8c536fd539b62f7af5b0da1130 Mon Sep 17 00:00:00 2001
From: uz <uz@b7a2c559-68d2-44c3-8de9-860c34a00d81>
Date: Thu, 4 Aug 2011 17:18:06 +0000
Subject: [PATCH] Adjust code to C99 regarding the main function: Not returning
 anything in a main function with an int return type is identical to returning
 zero.

git-svn-id: svn://svn.cc65.org/cc65/trunk@5118 b7a2c559-68d2-44c3-8de9-860c34a00d81
---
 src/cc65/function.c | 29 ++++++++++++++++++++++++-----
 src/cc65/function.h |  3 +++
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/src/cc65/function.c b/src/cc65/function.c
index 8944d1007..0f3229084 100644
--- a/src/cc65/function.c
+++ b/src/cc65/function.c
@@ -359,7 +359,7 @@ static void F_RestoreRegVars (Function* F)
 }
 
 
-    
+
 /*****************************************************************************/
 /*     	      	  	    	     code	      		 	     */
 /*****************************************************************************/
@@ -369,7 +369,8 @@ static void F_RestoreRegVars (Function* F)
 void NewFunc (SymEntry* Func)
 /* Parse argument declarations and function body. */
 {
-    SymEntry* Param;
+    int         C99MainFunc = 0;/* Flag for C99 main function returning int */
+    SymEntry*   Param;
 
     /* Get the function descriptor from the function entry */
     FuncDesc* D = Func->V.F.Func;
@@ -434,6 +435,14 @@ void NewFunc (SymEntry* Func)
         if (D->ParamCount > 0 || (D->Flags & FD_VARIADIC) != 0) {
             g_importmainargs ();
         }
+
+        /* Determine if this is a main function in a C99 environment that
+         * returns an int.
+         */
+        if (IsTypeInt (F_GetReturnType (CurrentFunc)) &&
+            IS_Get (&Standard) == STD_C99) {
+            C99MainFunc = 1;
+        }
     }
 
     /* Allocate code and data segments for this function */
@@ -517,13 +526,23 @@ void NewFunc (SymEntry* Func)
         Statement (0);
     }
 
-    /* If this is not a void function, output a warning if we didn't see a
-     * return statement.
+    /* If this is not a void function, and not the main function in a C99
+     * environment returning int, output a warning if we didn't see a return
+     * statement.
      */
-    if (!F_HasVoidReturn (CurrentFunc) && !F_HasReturn (CurrentFunc)) {
+    if (!F_HasVoidReturn (CurrentFunc) && !F_HasReturn (CurrentFunc) && !C99MainFunc) {
         Warning ("Control reaches end of non-void function");
     }
 
+    /* If this is the main function in a C99 environment returning an int, let
+     * it always return zero. Note: Actual return statements jump to the return
+     * label defined below.
+     * The code is removed by the optimizer if unused.
+     */
+    if (C99MainFunc) {
+        g_getimmed (CF_INT | CF_CONST, 0, 0);
+    }
+
     /* Output the function exit code label */
     g_defcodelabel (F_GetRetLab (CurrentFunc));
 
diff --git a/src/cc65/function.h b/src/cc65/function.h
index de9fdc123..36dcb0528 100644
--- a/src/cc65/function.h
+++ b/src/cc65/function.h
@@ -79,6 +79,9 @@ void F_ReturnFound (Function* F);
 int F_HasReturn (const Function* F);
 /* Return true if the function contains a return statement*/
 
+int F_IsMainFunc (const Function* F);
+/* Return true if this is the main function */
+
 int F_IsVariadic (const Function* F);
 /* Return true if this is a variadic function */