In IA32ABI plugin on 32-bit (x86/IA32) platforms, use -O0 in thunkEntry when compiling via gcc to not mess it up. Works fine with clang.

For 32-bit Windows builds via Cygwin/MSYS/MinGW, default to clang instead of gcc for the above reasons.

Also see (merged) PR #353.

Author: marceltaeumel

building/win32x86/common/Makefile.tools

@@ -9,7 +9,7 @@ export TOOLPREFIX
 # C compiler settings (gcc 4.x)
 #
 ifeq ($(COMPILER_TO_USE),)
-COMPILER_TO_USE:=gcc
+COMPILER_TO_USE:=clang
 endif
 
 ifeq ($(COMPILER_TO_USE),clang)

platforms/Cross/plugins/IA32ABI/ia32abicc.c

@@ -147,16 +147,14 @@ getMostRecentCallbackContext() { return mostRecentCallbackContext; }
  * args would get copied into a struct on the stack. A pointer to the struct
  * is then passed as an element of the VMCallbackContext.
  *
- * N.B. On gcc 7.4.x thunkEntry fails if optimized, for as yet not fully
+ * N.B. On gcc, thunkEntry fails if optimized, for as yet not fully
  * diagnosed reasons.  See
  *     https://github.com/OpenSmalltalk/opensmalltalk-vm/pull/353
- * Hence the pragma below.
+ * Hence the pragma below. Works fine for clang.
  */
 long
-#ifdef __GNUC__
-#  if __GNUC__ == 7 && __GNUC_MINOR__ >= 4
+#if defined(__GNUC__) && !defined(__clang__)
 __attribute__((optimize("O0")))
-#  endif
 #endif
 thunkEntry(void *thunkp, sqIntptr_t *stackp)
 {