Merge pull request #1927 from kaspar030/add_lto_flags

make: optionally build with gcc's link time optimization

Makefile.cflags

@@ -41,3 +41,9 @@ endif
 
 # Unwanted flags for c++
 CXXUWFLAGS += -std=%
+
+ifeq ($(LTO),yes)
+  LTOFLAGS = -flto -ffat-lto-objects
+  CFLAGS += ${LTOFLAGS}
+  LINKFLAGS += ${LTOFLAGS}
+endif

cpu/stm32f1/startup.c

@@ -188,7 +188,7 @@ void isr_dma2_ch4_5(void)     __attribute__ ((weak, alias("dummy_handler")));
 
 
 /* interrupt vector table */
-__attribute__ ((section(".vectors")))
+__attribute__ ((section(".vectors"))) __attribute__((used))
 const void *interrupt_vector[] = {
     /* Stack pointer */
     (void*) (&_estack),             /* pointer to the top of the empty stack */