10468 __ctype_mask[EOF] has been working by accident
10469 GCC's -faggressive-loop-optimizations is too aggressive
10470 array over-read in has_saved_fp()
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: John Levon <john.levon@joyent.com>

@@ -370,10 +370,21 @@
 # but the application of this may move into usr/src/uts/ in future.
 CCNOREORDER=    \
         -_gcc7=-fno-reorder-functions \
         -_gcc8=-fno-reorder-functions
 
+#
+# gcc has a rather aggressive optimization on by default that infers loop
+# bounds based on undefined behavior (!!).  This can lead to some VERY
+# surprising optimizations -- ones that may be technically correct in the
+# strictest sense but also result in incorrect program behavior.  We turn
+# this optimization off, with extreme prejudice.
+#
+CCNOAGGRESSIVELOOPS= \
+        -_gcc7=-fno-aggressive-loop-optimizations \
+        -_gcc8=-fno-aggressive-loop-optimizations
+
 # One optimization the compiler might perform is to turn this:
 #       #pragma weak foo
 #       extern int foo;
 #       if (&foo)
 #               foo = 5;

@@ -599,14 +610,16 @@
 $(SRCDBGBLD)CCSOURCEDEBUGFLAGS  = $(CCGDEBUG) -xs
 
 CFLAGS=         $(COPTFLAG) $($(MACH)_CFLAGS) $(SPACEFLAG) $(CCMODE) \
                 $(ILDOFF) $(CERRWARN) $(CSTD) $(CCUNBOUND) $(IROPTFLAG) \
                 $(CGLOBALSTATIC) $(CCNOAUTOINLINE) $(CCNOREORDER) \
+                $(CCNOAGGRESSIVELOOPS) \
                 $(CSOURCEDEBUGFLAGS) $(CUSERFLAGS)
 CFLAGS64=       $(COPTFLAG64) $($(MACH64)_CFLAGS) $(SPACEFLAG64) $(CCMODE64) \
                 $(ILDOFF) $(CERRWARN) $(CSTD) $(CCUNBOUND) $(IROPTFLAG64) \
                 $(CGLOBALSTATIC) $(CCNOAUTOINLINE) $(CCNOREORDER) \
+                $(CCNOAGGRESSIVELOOPS) \
                 $(CSOURCEDEBUGFLAGS) $(CUSERFLAGS64)
 #
 # Flags that are used to build parts of the code that are subsequently
 # run on the build machine (also known as the NATIVE_BUILD).
 #