use -nostdlib everywhere and improve ARCH detection

Makefile

@@ -1,49 +1,77 @@
-TARGET    = x64
-SUBSYSTEM = 10  # 10 = EFI application
-
-ifeq ($(TARGET),x64)
-	ARCH          = x86_64
-	GCC_ARCH      = x86_64
-	QEMU_ARCH     = x86_64
-	CROSS_COMPILE = $(GCC_ARCH)-w64-mingw32-
-	EP_PREFIX     =
-	CFLAGS        = -m64 -mno-red-zone
-	LDFLAGS	      = -Wl,-dll -Wl,--subsystem,$(SUBSYSTEM) -nostdlib
-else ifeq ($(TARGET),ia32)
-	ARCH          = ia32
-	GCC_ARCH      = i686
-	QEMU_ARCH     = i386
-	CROSS_COMPILE = $(GCC_ARCH)-w64-mingw32-
-	EP_PREFIX     = _
-	CFLAGS       = -m32 -mno-red-zone
-	# Can't use -nostdlib as we're missing an implementation of __umoddi3
-	# and __udivdi3, required by ia32/math.c and present in libgcc.a
-	LDFLAGS	      = -Wl,-dll -Wl,--subsystem,$(SUBSYSTEM)
-else ifeq ($(TARGET),arm)
-	ARCH          = arm
-	GCC_ARCH      = arm
-	QEMU_ARCH     = arm
-	CROSS_COMPILE = $(GCC_ARCH)-linux-gnueabihf-
-	EP_PREFIX     =
-	CFLAGS        = -marm -fpic -fshort-wchar
-	LDFLAGS       = -Wl,--no-wchar-size-warning -Wl,--subsystem,$(SUBSYSTEM) -nostdlib
+ARCH            = x64
+SUBSYSTEM       = 10  # 10 = EFI application
+
+# Try to auto-detect the target ARCH
+ifeq ($(shell uname -o),Msys)
+  IS_MINGW32 = $(findstring MINGW32,$(shell uname -s))
+  IS_MINGW64 = $(findstring MINGW64,$(shell uname -s))
+  ifeq ($(IS_MINGW32),MINGW32)
+    ARCH        = ia32
+  endif
+  ifeq ($(IS_MINGW64),MINGW64)
+    ARCH        = x64
+  endif
+else
+  ifeq ($(shell uname -m),x86_64)
+    ARCH        = x64
+  else ifeq ($(shell uname -m),arm)
+    ARCH        = arm
+    CROSS_COMPILE =
+  else
+    ARCH        = ia32
+  endif
 endif
 
-# Set parameters according to our platform
-ifeq ($(SYSTEMROOT),)
-  QEMU = qemu-system-$(QEMU_ARCH) -nographic
+# Auto-detect the host arch for MinGW
+ifeq ($(shell uname -m),x86_64)
+  MINGW_HOST    = w64
 else
+  MINGW_HOST    = w32
+endif
+
+ifeq ($(ARCH),x64)
+  GNUEFI_ARCH   = x86_64
+  GCC_ARCH      = x86_64
+  QEMU_ARCH     = x86_64
+  CROSS_COMPILE = $(GCC_ARCH)-$(MINGW_HOST)-mingw32-
+  EP_PREFIX     =
+  CFLAGS        = -m64 -mno-red-zone
+  LDFLAGS       = -Wl,-dll
+else ifeq ($(ARCH),ia32)
+  GNUEFI_ARCH   = ia32
+  GCC_ARCH      = i686
+  QEMU_ARCH     = i386
+  CROSS_COMPILE = $(GCC_ARCH)-$(MINGW_HOST)-mingw32-
+  EP_PREFIX     = _
+  CFLAGS        = -m32 -mno-red-zone
+  LDFLAGS       = -Wl,-dll
+else ifeq ($(ARCH),arm)
+  GNUEFI_ARCH   = arm
+  GCC_ARCH      = arm
+  QEMU_ARCH     = arm
+  CROSS_COMPILE = $(GCC_ARCH)-linux-gnueabi-
+  EP_PREFIX     =
+  CFLAGS        = -marm -fpic -fshort-wchar
+  LDFLAGS       = -Wl,--no-wchar-size-warning
+endif
+OVMF_ARCH       = $(shell echo $(ARCH) | tr a-z A-Z)
+
+# SYSTEMROOT is only defined on Windows systems
+ifneq ($(SYSTEMROOT),)
   QEMU = "/c/Program Files/qemu/qemu-system-$(QEMU_ARCH)w.exe"
+  # MinGW on Windows doesn't use (tuple)-ar but (tuple)-gcc-ar
+  # so we remove the cross compiler tuple altogether
   CROSS_COMPILE =
+else
+  QEMU = qemu-system-$(QEMU_ARCH) -nographic
 endif
-OVMF_ARCH   = $(shell echo $(TARGET) | tr a-z A-Z)
-GNUEFI_PATH = $(CURDIR)/gnu-efi
+GNUEFI_DIR = $(CURDIR)/gnu-efi
 
 CC     := $(CROSS_COMPILE)gcc
 CFLAGS += -fno-stack-protector -Wshadow -Wall -Wunused -Werror-implicit-function-declaration
-CFLAGS += -I$(GNUEFI_PATH)/inc -I$(GNUEFI_PATH)/inc/$(ARCH) -I$(GNUEFI_PATH)/inc/protocol
-LDFLAGS+= -shared -e $(EP_PREFIX)EfiMain
-LIBS   := -L$(GNUEFI_PATH)/$(ARCH)/lib -lefi
+CFLAGS += -I$(GNUEFI_DIR)/inc -I$(GNUEFI_DIR)/inc/$(GNUEFI_ARCH) -I$(GNUEFI_DIR)/inc/protocol
+LDFLAGS+= -Wl,--subsystem,$(SUBSYSTEM) -nostdlib -shared -e $(EP_PREFIX)EfiMain
+LIBS   := -L$(GNUEFI_DIR)/$(GNUEFI_ARCH)/lib -lefi
 
 OVMF_ZIP = OVMF-$(OVMF_ARCH)-r15214.zip
 
@@ -56,7 +84,7 @@ GCCMINOR   := $(shell $(CC) -dumpversion | cut -f2 -d.)
 GCCMACHINE := $(shell $(CC) -dumpmachine)
 GCCNEWENOUGH := $(shell ( [ $(GCCVERSION) -gt "4" ]           \
                           || ( [ $(GCCVERSION) -eq "4" ]      \
-                              && [ $(GCCMINOR) -ge "7" ] ) ) \
+                              && [ $(GCCMINOR) -ge "7" ] ) )  \
                         && echo 1)
 ifneq ($(GCCNEWENOUGH),1)
   $(error You need GCC 4.7 or later)
@@ -70,10 +98,10 @@ endif
 .PHONY: all clean superclean
 all: boot.efi
 
-$(GNUEFI_PATH)/$(ARCH)/lib/libefi.a:
-	$(MAKE) -C$(GNUEFI_PATH) CROSS_COMPILE=$(CROSS_COMPILE) ARCH=$(ARCH) lib
+$(GNUEFI_DIR)/$(GNUEFI_ARCH)/lib/libefi.a:
+	$(MAKE) -C$(GNUEFI_DIR) CROSS_COMPILE=$(CROSS_COMPILE) ARCH=$(GNUEFI_ARCH) lib
 
-%.efi: %.o $(GNUEFI_PATH)/$(ARCH)/lib/libefi.a
+%.efi: %.o $(GNUEFI_DIR)/$(GNUEFI_ARCH)/lib/libefi.a
 	@echo  [LD]  $(notdir $@)
 	@$(CC) $(LDFLAGS) $< -o $@ $(LIBS)
 
@@ -82,18 +110,18 @@ $(GNUEFI_PATH)/$(ARCH)/lib/libefi.a:
 	@$(CC) $(CFLAGS) -ffreestanding -c $<
 
 qemu: CFLAGS += -D_DEBUG
-qemu: boot.efi OVMF_$(OVMF_ARCH).fd ntfs.vhd image/efi/boot/boot$(TARGET).efi image/efi/rufus/ntfs_$(TARGET).efi
+qemu: boot.efi OVMF_$(OVMF_ARCH).fd ntfs.vhd image/efi/boot/boot$(ARCH).efi image/efi/rufus/ntfs_$(ARCH).efi
 	$(QEMU) -bios ./OVMF_$(OVMF_ARCH).fd -net none -hda fat:image -hdb ntfs.vhd
 
-image/efi/boot/boot$(TARGET).efi: boot.efi
+image/efi/boot/boot$(ARCH).efi: boot.efi
 	mkdir -p image/efi/boot
 	cp -f $< $@
 
 # NTFS driver
-ntfs_$(TARGET).efi:
-	wget http://efi.akeo.ie/downloads/efifs-0.8/$(ARCH)/ntfs_$(TARGET).efi
+ntfs_$(ARCH).efi:
+	wget http://efi.akeo.ie/downloads/efifs-0.8/$(ARCH)/ntfs_$(ARCH).efi
 
-image/efi/rufus/ntfs_$(TARGET).efi: ntfs_$(TARGET).efi
+image/efi/rufus/ntfs_$(ARCH).efi: ntfs_$(ARCH).efi
 	mkdir -p image/efi/rufus
 	cp -f $< $@
 
@@ -111,9 +139,10 @@ OVMF_$(OVMF_ARCH).fd:
 	rm $(OVMF_ZIP)
 
 clean:
+	$(MAKE) -C$(GNUEFI_DIR) clean
 	rm -f boot.efi *.o
 	rm -rf image
 
 superclean: clean
-	$(MAKE) -C$(GNUEFI_PATH) clean
+	$(MAKE) -C$(GNUEFI_DIR) clean
 	rm -f *.fd ntfs.vhd ntfs_*.efi

README.md

@@ -52,11 +52,14 @@ git submodule update
 If using Visual Studio, just press `F5` to have the application compiled and
 launched in the QEMU emulator.
 
-If using MinGW, issue: `make TARGET=<arch>` where `<arch>` is one of `ia32`
-or `x64`. You can also debug through QEMU with MinGW by adding `qemu` to your
-`make` invocation. Be mindful however that this turns the special `_DEBUG`
-mode on, and you should run make without invoking `qemu` to produce proper
-release binaries.
+If using gcc, you should be able to simply issue `make`. If needed you can also
+issue something like `make ARCH=<arch> CROSS_COMPILE=<tuple>` where `<arch>` is
+one of `ia32`, `x64` or `arm` and tuple is the one for your cross-compiler (e.g.
+`arm-linux-gnueabihf-`).
+
+You can also debug through QEMU by specifying `qemu` to your `make` invocation.
+Be mindful however that this turns the special `_DEBUG` mode on, and you should
+run make without invoking `qemu` to produce proper release binaries.
 
 ## Download and installation