cortexm_common_ldscript: add test for _fw_rom_length overflow

Verify that specifying a too big _fw_rom_length for the rom is detected and
prevent compilation.

tests/cortexm_common_ldscript/Makefile

@@ -25,7 +25,7 @@ include $(RIOTBASE)/Makefile.include
 # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
 COMPILE_TESTS  = test-elffile-overflow test-elffile-fw_rom_length
-COMPILE_TESTS += tests-offsets tests-fw_rom_len
+COMPILE_TESTS += tests-offsets tests-fw_rom_len tests-rom-overflow
 
 all: compile-tests
 
@@ -121,3 +121,24 @@ $(BINDIR)/$(APPLICATION)_fw_len_half_rom.elf: FW_ROM_LEN=$$(($(ROM_LEN_BYTES)/2)
 $(BINDIR)/$(APPLICATION)_fw_len_half_rom.elf: $(ELFFILES_DEPS)
 	$(Q)$(_LINK) -o $@
 .PRECIOUS: $(BINDIR)/$(APPLICATION)_fw_len_half_rom.elf
+
+
+# Test FW_ROM_LEN overflow detection
+
+OVERFLOW_TESTS = too_big_for_rom offset_and_romlen
+tests-rom-overflow: $(OVERFLOW_TESTS:%=test-assert_overflow_%)
+
+
+# Simple FW_ROM_LEN overflow
+test-assert_overflow_too_big_for_rom: FW_ROM_LEN=$$(($(ROM_LEN_BYTES) + 1))
+
+# ROM_OFFSET and FW_ROM_LEN set ROM_LEN
+test-assert_overflow_offset_and_romlen: ROM_OFFSET=0x1000
+test-assert_overflow_offset_and_romlen: FW_ROM_LEN=$(ROM_LEN_BYTES)
+
+.PHONY: test-assert_overflow_%
+test-assert_overflow_%: $(ELFFILES_DEPS)
+	$(Q) echo -n "Test ROM overflow detection ($*): "
+	$(Q)\
+	{ $(_LINK) -o /dev/null 2>&1 | grep -q 'Specified firmware size does not fit in ROM' ; } \
+	  && echo [OK] || { echo [ERROR] Compilation should have failed >&2; exit 1; }