From 545b0be96eff545caccf2335f596f9ad8d6b0c05 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?King=20K=C3=A9vin?= <kingkevin@cuvoodoo.info>
Date: Sat, 20 Aug 2016 18:10:31 +0200
Subject: [PATCH] use clang to compile

---
 Makefile | 55 ++++++++++++++++++++++++++++++++++---------------------
 main.c   |  8 +++-----
 2 files changed, 37 insertions(+), 26 deletions(-)

diff --git a/Makefile b/Makefile
index 0166c4a..e376d2b 100644
--- a/Makefile
+++ b/Makefile
@@ -45,15 +45,21 @@ LIB_OBJ = $(patsubst %.c,%.o,$(LIB_CSRC))
 # populates LIB_CSRC based on the library files used
 -include $(DEPENDENCIES)
 
-# executables
+# cross-compiler tools
 PREFIX ?= arm-none-eabi
+# compile using gcc (requires gcc-arm-none-eabi)
 CC := $(PREFIX)-gcc
-CXX := $(PREFIX)-g++
-LD := $(PREFIX)-gcc
+# compile using clang (requires clang gcc-multilib)
+CC := clang -target $(PREFIX)
+# link (requires binutils-arm-none-eabi)
+LD := $(PREFIX)-ld
+# create archive (requires binutils-arm-none-eabi)
 AR := $(PREFIX)-ar
+# compile assembly (requires binutils-arm-none-eabi)
 AS := $(PREFIX)-as
 OBJCOPY := $(PREFIX)-objcopy
 OBJDUMP := $(PREFIX)-objdump
+# debugger (requires)
 GDB := $(PREFIX)-gdb
 
 # opencm3 libraries
@@ -82,31 +88,38 @@ endif
 DEFS += -DSTM32F1 -D$(BOARD)
 
 # C flags
-CFLAGS += -Os -g
-CFLAGS += -std=c99 -Wpedantic -Wall -Werror -Wundef -Wextra -Wshadow -Wredundant-decls -Wmissing-prototypes -Wstrict-prototypes -Wstrict-overflow=5
+CFLAGS += -Os -g -std=c99 -nostdlib
+# TODO try to get rid of system libraries (and use -ffreestanding)
 CFLAGS += -fno-common -ffunction-sections -fdata-sections
+CFLAGS += -Wpedantic -Wall -Werror -Wundef -Wextra -Wshadow -Wredundant-decls -Wmissing-prototypes -Wstrict-prototypes -Wstrict-overflow=5
 CFLAGS += -I. -I$(INCLUDE_DIR) $(patsubst %,-I%,$(LIB))
 CFLAGS += $(DEFS)
 
 # linker flags
-LDFLAGS += --static -nostartfiles
-LDFLAGS += -L$(LIB_DIR)
-LDFLAGS += -I. $(patsubst %,-I%,$(LIB))
-LDFLAGS += -T$(LDSCRIPT)
-LDFLAGS += -Wl,-Map=$(*).map
-LDFLAGS += -Wl,--gc-sections
-ifeq ($(V),99)
-LDFLAGS += -Wl,--print-gc-sections
-endif
-
-# used libraries
+LDFLAGS += -static -nostartfiles -nostdlib
+# opencm3 libraries
+LDFLAGS += --library-path $(LIB_DIR)
 LIBNAME = opencm3_stm32f1
-LDLIBS += -lm -l$(LIBNAME)
-LDLIBS += -Wl,--start-group -lc -lgcc -lnosys -Wl,--end-group
+LDLIBS += --library $(LIBNAME)
+# TODO use newlib (providing libc, libm, and libg/libnosys) and get rib of the libgcc
+# curiously newlib seems to require libgcc (In function `_vfprintf_r': undefined reference to `__aeabi_dcmplt')
+# also even with libcc aliases are missing (In function `cdcacm_data_rx_cb': undefined reference to `__aeabi_memset')
+#LDFLAGS += --library-path /usr/lib/arm-none-eabi/newlib/armv7-m/
+# provides libgcc
+# TODO retrieve path automatically (arm-none-eabi-gcc does it on its own)
+LDFLAGS += --library-path /usr/lib/gcc/arm-none-eabi/*/armv7-m/
+# provides libc, libm, libnosys
+# TODO retrieve path automatically (arm-none-eabi-gcc does it on its own)
+LDFLAGS += --library-path /usr/arm-none-eabi/lib/armv7-m/
+# own libraries
+LDFLAGS += --dynamic-linker . $(patsubst %,--dynamic-linker %,$(LIB))
+# libc and other system libraries
+LDLIBS += --library c --library gcc --library nosys --library m
+# linker script for micro-controller
+LDFLAGS += -T $(LDSCRIPT)
 
 # device specific flags
-FP_FLAGS ?= -msoft-float
-ARCH_FLAGS = -mthumb -mcpu=cortex-m3 $(FP_FLAGS) -mfix-cortex-m3-ldrd
+ARCH_FLAGS = -mthumb -mcpu=cortex-m3
 
 # SWD adapter used
 # supported are : st-link v2 (STLINKV2), black magic probe (BMP)
@@ -146,7 +159,7 @@ list: $(BINARY).list
 
 %.elf: $(LDSCRIPT) $(LIB_DIR)/lib$(LIBNAME).a $(OBJ) $(LIB_OBJ)
 	$(info compiling $(@))
-	$(Q)$(LD) $(LDFLAGS) $(ARCH_FLAGS) $(OBJ) $(LIB_OBJ) $(LDLIBS) -o $(@)
+	$(Q)$(LD) $(LDFLAGS) $(OBJ) $(LIB_OBJ) $(LDLIBS) -o $(@)
 	$(Q)size $(@)
 
 %.o: %.c $(CHDR) $(LIB_CHDR)
diff --git a/main.c b/main.c
index 7d85fd2..861676a 100644
--- a/main.c
+++ b/main.c
@@ -25,7 +25,6 @@
 #include <unistd.h> // standard streams
 #include <string.h> // string utilities
 #include <math.h> // mathematical utilities
-#include <errno.h> // error number utilities
 
 /* STM32 (including CM3) libraries */
 #include <libopencm3/stm32/rcc.h> // real-time control clock library
@@ -40,7 +39,7 @@
 #include "global.h" // board definitions
 #include "usart.h" // USART utilities
 #include "usb_cdcacm.h" // USB CDC ACM utilities
-#include "usart_soft.h" // software USART utilities
+#include "uart_soft.h" // software USART utilities
 
 /** @defgroup main_flags flag set in interrupts to be processed in main task
  *  @{
@@ -74,7 +73,6 @@ int _write(int file, char *ptr, int len)
 		}
 		return i;
 	}
-	errno = EIO;
 	return -1;
 }
 
@@ -147,8 +145,8 @@ int main(void)
 	// setup USART and USB for user communication
     usart_setup(); // setup USART (for printing)
 	cdcacm_setup(); // setup USB CDC ACM (for printing)
-    setbuf(stdout, NULL); // set standard out buffer to NULL to immediately print   
-    setbuf(stderr, NULL); // set standard error buffer to NULL to immediately print
+	//setbuf(stdout, NULL); // set standard out buffer to NULL to immediately print
+	//setbuf(stderr, NULL); // set standard error buffer to NULL to immediately print
 
 	// minimal setup ready	
 	printf("welcome to the STM32F1 CuVoodoo example code\n"); // print welcome message