This is needed for compatibility with future C compilers which reject implicit function declarations by default. Without _GNU_SOURCE (or a similar feature test macro), <time.h> does not declare the strptime function, and compilation can fail. --- Make.rules | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Make.rules b/Make.rules index 903a5a4..d4de1ef 100644 --- a/Make.rules +++ b/Make.rules @@ -14,7 +14,7 @@ else $(error unknown architecture $(ARCH)) endif INCDIR = -I$(TOPDIR)include/ -I/usr/include/efi -I/usr/include/efi/$(ARCH) -I/usr/include/efi/protocol -CPPFLAGS = -DCONFIG_$(ARCH) +CPPFLAGS = -DCONFIG_$(ARCH) -D_GNU_SOURCE CFLAGS = -O2 -g $(ARCH3264) -fpic -Wall -fshort-wchar -fno-strict-aliasing -fno-merge-constants -fno-stack-protector -ffreestanding -fno-stack-check LDFLAGS = -nostdlib CRTOBJ = crt0-efi-$(ARCH).o Related to: <https://fedoraproject.org/wiki/Changes/PortingToModernC> <https://fedoraproject.org/wiki/Toolchain/PortingToModernC>
