From 5bc11922f1f8e0bfb27e8e260c7971405535c257 Mon Sep 17 00:00:00 2001 From: Bin Meng Date: Sun, 16 Sep 2018 22:35:28 -0700 Subject: [PATCH] Makefile: Use -fno-strict-aliasing globally The -fstrict-aliasing option is implicitly enabled at levels -O2, -O3, -Os by GCC. This option allows the compiler to assume the strictest aliasing rules applicable to the language being compiled. For example, the practice of reading from a different union member than the one most recently written to (called "type-punning") is common. In this case, "type-punning" only works if the memory is accessed through the union type, but might not work by taking the address, casting the resulting pointer and dereferencing the result, which is an undefined behavior per the "strict aliasing rules". GCC's -Wstrict-aliasing (included in -Wall) option does not catch all cases, but does attempt to catch the more common pitfalls. So there are cases that GCC does not report but the codes are violating the "strict aliasing rules". Given lots of codes that may be written to rely on "type-punning", and Linux kernel disables it by -fno-strict-aliasing globally, since U-Boot currently does this on nds32/riscv/x86 builds only, extend this for all architecture builds. Signed-off-by: Bin Meng Reviewed-by: Tom Rini Reviewed-by: Simon Glass --- Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Makefile b/Makefile index e38966e..3561fb0 100644 --- a/Makefile +++ b/Makefile @@ -372,7 +372,7 @@ KBUILD_CPPFLAGS := -D__KERNEL__ -D__UBOOT__ KBUILD_CFLAGS := -Wall -Wstrict-prototypes \ -Wno-format-security \ -fno-builtin -ffreestanding $(CSTD_FLAG) -KBUILD_CFLAGS += -fshort-wchar +KBUILD_CFLAGS += -fshort-wchar -fno-strict-aliasing KBUILD_AFLAGS := -D__ASSEMBLY__ # Don't generate position independent code