这里写图片描述

虽然当前android啥的是主流,但是在进行裸机开发的时候,熟悉编译器这些参数就很重要了。下面以uboot的编译和链接过程为实例介绍arm gcc相关的参数。具体内容可以参考

官方文档: https://gcc.gnu.org/onlinedocs/
pdf版本下载:https://gcc.gnu.org/onlinedocs/gcc-4.8.5/gcc.pdf

编译参数

arm-none-linux-gnueabi-gcc -Wp,-MD,common/.main.o.d  -nostdinc -isystem /home/camus/arm-2014.05/bin/../lib/gcc/arm-none-linux-gnueabi/4.8.3/include -Iinclude  -I./arch/arm/include -include ./include/linux/kconfig.h -D__KERNEL__ -D__UBOOT__ -Wall -Wstrict-prototypes -Wno-format-security -fno-builtin -ffreestanding -Os -fno-stack-protector -fstack-usage -Wno-format-nonliteral -D__ARM__ -marm -mno-thumb-interwork -mabi=aapcs-linux -mword-relocations -mno-unaligned-access -ffunction-sections -fdata-sections -fno-common -ffixed-r9 -msoft-float -pipe -march=armv7-a    -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(main)"  -D"KBUILD_MODNAME=KBUILD_STR(main)" -c -o common/main.o common/main.c
  • -Wp,-MD,common/.main.o.d (给预处理器传递option)
  • -nostdinc (不搜索系统头文件==只搜索-I指定的目录以及当前文件所在目录)
  • -isystem /home/camus/arm-2014.05/bin/../lib/gcc/arm-none-linux-gnueabi/4.8.3/include (指定搜索头文件的目录,优先级在-I后,但是在系统头文件前)
  • -Iinclude (-I: 指定头文件搜索目录include)
  • -I./arch/arm/include (指定头文件搜索目录)
  • -include ./include/linux/kconfig.h (包含指定头文件,类似于在源文件第一行添加#include “file”)
  • -D__KERNEL__ -D__UBOOT__ (编译时使能宏)
  • -Wall -Wstrict-prototypes -Wno-format-security (打开all warning,具体包含哪些参见手册)
  • -fno-builtin (只把以_builtin开头的函数当成内建函数)
  • -ffreestanding (不约定标准库和程序入口==-fno-hosted)
  • -Os (优化等级super)
  • -fno-stack-protector (不了解)
  • -fstack-usage (生成stack使用信息,su文件)
  • -Wno-format-nonliteral (不知道)
  • -D__ARM__ (定义宏ARM
  • -marm (和-mthumb用来执行生成的代码在arm模式还是thumb模式执行)
  • -mno-thumb-interwork (没有ARM/Thumb之间的切换)
  • -mabi=aapcs-linux (针对不同系统的调用规则生成代码)
  • -mword-relocations (只对size为word倍数的变量分配绝对地址)
  • -mno-unaligned-access (访问对齐限制)
  • -ffunction-sections (把每个函数放入单独的section中,如果目标文件支持任意数量section)
  • -fdata-sections (同上,只是对象是数据)
  • -fno-common (放置未初始化的全局变量,这里不放到common block中,而是放到data section中)
  • -ffixed-r9 (生成的代码不要用寄存器r9,uboot中用来指向global data)
  • -msoft-float (软件模拟浮点运算,默认选项)
  • -pipe (在compilation stages之间通过pipe通信)
  • -march=armv7-a (指定目标体系结构)
  • -D”KBUILD_STR(s)=#s” (定义宏)
  • -D”KBUILD_BASENAME=KBUILD_STR(main)” (同上)
  • -D”KBUILD_MODNAME=KBUILD_STR(main)” (同上)
  • -c (只生成目标文件)
  • -o common/main.o (目标文件重命名)
  • common/main.c (源文件路径)

链接参数

arm-none-linux-gnueabi-ld   -pie  --gc-sections -Bstatic -Ttext 0x43e00000 -o u-boot -T u-boot.lds arch/arm/cpu/armv7/start.o --start-group  arch/arm/cpu/built-in.o  arch/arm/cpu/armv7/built-in.o  arch/arm/lib/built-in.o  board/samsung/common/built-in.o  board/samsung/landrover/built-in.o  common/built-in.o  disk/built-in.o  drivers/built-in.o  drivers/dma/built-in.o  drivers/gpio/built-in.o  drivers/i2c/built-in.o  drivers/mmc/built-in.o  drivers/mtd/built-in.o  drivers/mtd/onenand/built-in.o  drivers/mtd/spi/built-in.o  drivers/net/built-in.o  drivers/net/phy/built-in.o  drivers/pci/built-in.o  drivers/power/built-in.o  drivers/power/battery/built-in.o  drivers/power/fuel_gauge/built-in.o  drivers/power/mfd/built-in.o  drivers/power/pmic/built-in.o  drivers/serial/built-in.o  drivers/spi/built-in.o  drivers/usb/eth/built-in.o  drivers/usb/gadget/built-in.o  drivers/usb/host/built-in.o  drivers/usb/musb-new/built-in.o  drivers/usb/musb/built-in.o  drivers/usb/phy/built-in.o  drivers/usb/ulpi/built-in.o  dts/built-in.o  fs/built-in.o  lib/built-in.o  net/built-in.o  test/built-in.o  test/dm/built-in.o --end-group arch/arm/lib/eabi_compat.o  -L /home/camus/arm-2014.05/bin/../lib/gcc/arm-none-linux-gnueabi/4.8.3 -lgcc -Map u-boot.map
  • -pie (生成位置无关position independent executable)
  • –gc-sections (不知道)
  • -Bstatic (和-Bdynamic,为了和Diab?兼容)
  • -Ttext 0x43e00000 (指定代码段地址)
  • -o u-boot (目标重命名)
  • -T u-boot.lds (指定链接脚本)
  • arch/arm/cpu/armv7/start.o (要链接的文件)
  • –start-group (不知)
  • arch/arm/cpu/built-in.o arch/arm/cpu/armv7/built-in.o arch/arm/lib/built-in.o board/samsung/common/built-in.o board/samsung/landrover/built-in.o common/built-in.o disk/built-in.o drivers/built-in.o drivers/dma/built-in.o drivers/gpio/built-in.o drivers/i2c/built-in.o drivers/mmc/built-in.o drivers/mtd/built-in.o drivers/mtd/onenand/built-in.o drivers/mtd/spi/built-in.o drivers/net/built-in.o drivers/net/phy/built-in.o drivers/pci/built-in.o drivers/power/built-in.o drivers/power/battery/built-in.o drivers/power/fuel_gauge/built-in.o drivers/power/mfd/built-in.o drivers/power/pmic/built-in.o drivers/serial/built-in.o drivers/spi/built-in.o drivers/usb/eth/built-in.o drivers/usb/gadget/built-in.o drivers/usb/host/built-in.o drivers/usb/musb-new/built-in.o drivers/usb/musb/built-in.o drivers/usb/phy/built-in.o drivers/usb/ulpi/built-in.o dts/built-in.o fs/built-in.o lib/built-in.o net/built-in.o test/built-in.o test/dm/built-in.o (一大堆要链接的文件)
  • –end-group (同–start-group一起)
  • arch/arm/lib/eabi_compat.o (同样是要链接的文件)
  • -L /home/camus/arm-2014.05/bin/../lib/gcc/arm-none-linux-gnueabi/4.8.3 (library搜索目录)
  • -lgcc (指定libgcc.a)
  • -Map u-boot.map (指定存放最终镜像内存映射信息的文件)
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