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问 同样的代码
ICC编译后736字节 (版本icc AVR6.30 45天试用版)
GCC编译后1652字节 (版本win AVR20030310 )
在硬件上运行结果相同。
gcc优化级为 s
结果让我十分苦恼
我实在不愿看到这个结果(心爱的 GCC你不会是和我开玩笑呢吧！)。
就算插入初始化代码也不至于将近1K( 单片机一共没多少K呀)吧！
GCC高手们,请给我一个合理的解释好吗？

代码点下面链接下载后把扩展名改成RAR后解压缩。
http://www.21icsearch.com/buzi/upimage/upfile/2004422923170.jpg
答 1: 这里下http://bitfu.go.nease.net/temp/code.rar 答 2: 你的程序好像没用到printf函数所以可以修改一下链接编译选项

你的Makefile中
# Optional linker flags.
LDFLAGS = -Wl,-Map=$(TARGET).map,--cref,-u,vfprintf -lprintf_min
改为
# Optional linker flags.
LDFLAGS = -Wl,-Map=$(TARGET).map,--cref

# Additional libraries
#
# Minimalistic printf version
#LDFLAGS += -Wl,-u,vfprintf -lprintf_min
#
# Floating point printf version (requires -lm below)
#LDFLAGS += -Wl,-u,vfprintf -lprintf_flt
#
# -lm = math library
#LDFLAGS += -lm

可视情况添加或删减链接库文件
试试看，程序代码量应该会大大减少，比ICC少很多
（我没试，暂时不用 AVR，所以机子没装Win AVR） 答 3: 我换了makefile 编译后为510字节#makefile如下：

# Win AVRSample makefile written by Eric B. Weddington, Jörg Wunsch, et al.
# Released to the Public Domain
# Please read the make user manual!
#
#
# On command line:
#
# make all = Make software.
#
# make clean = Clean out built project files.
#
# make coff = Convert ELF to AVRCOFF (for use with AVRStudio 3.x or VMLAB).
#
# make extcoff = Convert ELF to AVRExtended COFF (for use with AVRStudio
# 4.07 or greater).
#
# make program = Download the hex file to the device, using AVRdude. Please
# customize the AVRdude settings below first!
#
# make filename.s = Just compile filename.c into the assembler code only
#
# To rebuild project do "make clean" then "make all".
#


#============= MCUÑ¡Ôñ ===========================
# MCU name
MCU = at90s8535

#============= Êä³ö¸ñʽѡÔñ ======================
# Output format. ( CANbe srec, ihex, binary)
FORMAT = ihex

#============= Ä¿±êÎļþÃû(²»´øÀ©Õ¹Ãû) ============
# Target file name (without extension).
TARGET = demo

#============= ÓÅ»¯¼¶±ðÑ¡Ôñ ======================
# Optimization level, CANbe [0, 1, 2, 3, s]. 0 turns off optimization.
# (Note: 3 is not always the best optimization level. See AVR-libc FAQ.)
OPT = s


#============= C Ô´ÎļþÁбí("\"Ϊ»»ÐзûºÅ) =======
# List C source files here. (C dependencies are automatically generated.)
SRC = $(TARGET).c

# If there is more than one source file, append them above, or adjust and
# uncomment the following:
#SRC += foo.c bar.c

# You CANalso wrap lines by appending a backslash to the end of the line:
#SRC += baz.c \
#xyzzy.c



#============= ASM Ô´ÎļþÁбí ====================
# List Assembler source files here.
# Make them always end in a capital .S. Files ending in a lowercase .s
# will not be considered source files but generated files (assembler
# output from the compiler), and will be deleted upon "make clean"!
# Even though the DOS/Win* filesystem matches both .s and .S the same,
# it will preserve the spelling of the filenames, and gcc itself does
# care about how the name is spelled on its command-line.
ASRC =




#============= C±àÒëÑ¡Ïî =========================
# Optional compiler flags.
# -g: generate debugging information (for GDB, or for COFF conversion)
# -O*: optimization level
# -f...: tuning, see gcc manual and AVR-libc documentation
# -Wall...: warning level
# -Wa,...: tell GCCto pass this to the assembler.
# -ahlms: create assembler listing
CFLAGS = -g -O$(OPT) \
-funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums \
-Wall -Wstrict-prototypes \
-Wa,-ahlms=$(<:.c=.lst)



#============= »ã±àÆ÷Ñ¡Ïî ========================
# Optional assembler flags.
# -Wa,...: tell GCCto pass this to the assembler.
# -ahlms: create listing
# -gstabs: have the assembler create line number information; note that
# for use in COFF files, additional information about filenames
# and function names needs to be present in the assembler source
# files -- see AVR-libc docs [FIXME: not yet described there]
ASFLAGS = -Wa,-ahlms=$(<:.S=.lst),-gstabs



#============= Á¬½ÓÆ÷Ñ¡Ïî ========================
# Optional linker flags.
# -Wl,...: tell GCCto pass this to linker.
# -Map: create map file
# --cref: add cross reference to map file
LDFLAGS = -Wl,-Map=$(TARGET).map,--cref



#============= ¸½¼Ó¿âÑ¡Ïî ========================
# Additional libraries
#
# Minimalistic printf version
#LDFLAGS += -Wl,-u,vfprintf -lprintf_min
#
# Floating point printf version (requires -lm below)
#LDFLAGS += -Wl,-u,vfprintf -lprintf_flt
#
# -lm = math library
LDFLAGS += -lm




# Programming support using AVRdude. Settings and variables.

# Programming hardware: AVRisp stk500 AVR910 p AVRstk200 pony-stk200
# dt006 bascom alf
# Type: AVRdude -c ?
# to get a full listing.
#
AVRDUDE_PROGRAMMER = stk500


AVRDUDE_PORT = com1 # programmer connected to serial device
# AVRDUDE_PORT = lpt1 # programmer connected to parallel port

AVRDUDE_ERASE = -e
AVRDUDE_FLAGS = -p $(MCU) -P $( AVRDUDE_PORT) -c $( AVRDUDE_PROGRAMMER)


# Uncomment the following if you want AVRdude's erase cycle counter.
# Note that this counter needs to be initialized first using -Yn,
# see AVRdude manual.
# AVRDUDE_ERASE += -y
#
# Uncomment the following if you do /not/ wish a verification to be
# performed after programming the device.
# AVRDUDE_FLAGS += -V
#
# Increase verbosity level. Please use this when submitting bug
# reports about AVRdude. See AVRdude>
# to submit bug reports.
# AVRDUDE_FLAGS += -v -v




# ---------------------------------------------------------------------------

#============= Ö¸¶¨Ä¿Â¼£¬Èç¹ûÐèÒª ================
# Define directories, if needed.
DIR AVR= c:/win AVR
DIR AVRBIN = $(DIR AVR)/bin
DIR AVRUTILS = $(DIR AVR)/utils/bin
DIRINC = .
DIRLIB = $(DIR AVR)/ AVR/lib


#============= ¶¨ÒåÃüÁî(¹¤¾ßÈí¼þÃû³Æ) ============
# Define programs and commands.
SHELL = sh

CC = AVR-gcc

OBJCOPY = AVR-objcopy
OBJDUMP = AVR-objdump
SIZE = AVR-size


# Programming support using AVRdude.
AVRDUDE = AVRdude


REMOVE = rm -f
COPY = cp

HEXSIZE = $(SIZE) --target=$(FORMAT) $(TARGET).hex
#ELFSIZE = $(SIZE) -A $(TARGET).elf
ELFSIZE = $(SIZE) $(TARGET).elf

FINISH = echo Errors: none
BEGIN = echo -------- begin --------
END = echo -------- end --------




# Define all object files.
OBJ = $(SRC:.c=.o) $(ASRC:.S=.o)

# Define all listing files.
LST = $(ASRC:.S=.lst) $(SRC:.c=.lst)

# Combine all necessary flags and optional flags.
# Add target processor to flags.
ALL_CFLAGS = -mmcu=$(MCU) -I. $(CFLAGS)
ALL_ASFLAGS = -mmcu=$(MCU) -I. -x assembler-with-cpp $(ASFLAGS)



# Default target.
all: begin gccversion sizebefore $(TARGET).elf $(TARGET).hex $(TARGET).eep \
$(TARGET).lss sizeafter finished end


# Eye CANdy.
# AVRStudio 3.x does not check make's exit code but relies on
# the following magic strings to be generated by the compile job.
begin:
@$(BEGIN)

finished:
@$(FINISH)

end:
@$(END)


# Display size of file.
sizebefore:
@if [ -f $(TARGET).elf ]; then echo Size before:; $(ELFSIZE);fi

sizeafter:
@if [ -f $(TARGET).elf ]; then echo Size after:; $(ELFSIZE);fi



# Display compiler version information.
gccversion :
$(CC) --version




# Convert ELF to COFF for use in debugging / simulating in
# AVRStudio or VMLAB.
COFFCONVERT=$(OBJCOPY) --debugging \
--change-section-address .data-0x800000 \
--change-section-address .bss-0x800000 \
--change-section-address .noinit-0x800000 \
--change-section-address .eeprom-0x810000


coff: $(TARGET).elf
$(COFFCONVERT) -O coff- AVR$< $(TARGET).cof


extcoff: $(TARGET).elf
$(COFFCONVERT) -O coff-ext- AVR$< $(TARGET).cof




# Program the device. The magic trickery below examines the .eep hex
# file whether the size is > 0, and if so, reprograms the EEPROM as
# well. Just delete these lines if you don't want this feature (like
# on the ATmegas with the EESAVE fuse bit set).
program: $(TARGET).hex $(TARGET).eep
$( AVRDUDE) $( AVRDUDE_FLAGS) $( AVRDUDE_ERASE)
$( AVRDUDE) $( AVRDUDE_FLAGS) -i $(TARGET).hex
@$(SIZE) --target=$(FORMAT) $(TARGET).eep | while read line; \
do \
set -- $$line; \
if [ "x$$1" != "x0" ] ; then continue; fi; \
if [ "$$2" -ne 0 ] ; then \
echo $( AVRDUDE) $( AVRDUDE_FLAGS) -m eeprom -i $(TARGET).eep; \
$( AVRDUDE) $( AVRDUDE_FLAGS) -m eeprom -i $(TARGET).eep; \
break; \
fi; \
done


# Create final output files (.hex, .eep) from ELF output file.
%.hex: %.elf
$(OBJCOPY) -O $(FORMAT) -R .eeprom $< $@

%.eep: %.elf
-$(OBJCOPY) -j .eeprom --set-section-flags=.eeprom="alloc,load" \
--change-section-lma .eeprom=0 -O $(FORMAT) $< $@

# Create extended listing file from ELF output file.
%.lss: %.elf
$(OBJDUMP) -h -S $< > $@



# Link: create ELF output file from object files.
.SECONDARY : $(TARGET).elf
.PRECIOUS : $(OBJ)
%.elf: $(OBJ)
$(CC) $(ALL_CFLAGS) $(OBJ) --output $@ $(LDFLAGS)


# Compile: create object files from C source files.
%.o : %.c
$(CC) -c $(ALL_CFLAGS) $< -o $@


# Compile: create assembler files from C source files.
%.s : %.c
$(CC) -S $(ALL_CFLAGS) $< -o $@


# Assemble: create object files from assembler source files.
%.o : %.S
$(CC) -c $(ALL_ASFLAGS) $< -o $@






# Target: clean project.
clean: begin clean_list finished end

clean_list :
$(REMOVE) $(TARGET).hex
$(REMOVE) $(TARGET).eep
$(REMOVE) $(TARGET).obj
$(REMOVE) $(TARGET).cof
$(REMOVE) $(TARGET).elf
$(REMOVE) $(TARGET).map
$(REMOVE) $(TARGET).obj
$(REMOVE) $(TARGET).a90
$(REMOVE) $(TARGET).sym
$(REMOVE) $(TARGET).lnk
$(REMOVE) $(TARGET).lss
$(REMOVE) $(OBJ)
$(REMOVE) $(LST)
$(REMOVE) $(SRC:.c=.s)
$(REMOVE) $(SRC:.c=.d)


# Automatically generate C source code dependencies.
# (Code originally taken from the GNU make user manual and modified
# (See README.txt Credits).)
#
# Note that this will work with sh (bash) and sed that is shipped with Win AVR
# (see the SHELL variable defined above).
# This may not work with other shells or other seds.
#
%.d: %.c
set -e; $(CC) -MM $(ALL_CFLAGS) $< \
| sed 's,\(.*\)\.o[ :]*,\1.o \1.d : ,g' > $@; \
[ -s $@ ] || rm -f $@


# Remove the '-' if you want to see the dependency files generated.
-include $(SRC:.c=.d)



# Listing of phony targets.
.PHONY : all begin finish end sizebefore sizeafter gccversion coff extcoff \
clean clean_list program


答 4: 确实是这样感谢 笑苍天、yfzhang。

我也试过了，那个MAKEFILE是WIN AVR里的示例，改时没有注意。

我很抱歉， GCC及它的爱好者们！