【工程师分享】MPSoC交叉编译例子

作者：付汉杰，hankf@xilinx.com，文章转载自：赛灵思中文社区论坛

1. 介绍
有工程师反馈,使用A53交叉编译器直接编译最简单的C文件,编译器也报告。"stdio.h: No such file or directory"

aarch64-xilinx-linux-gcc -c hello.c -DPLATFORM_ZCU106 -std=c11 -o hello.o
hello.c:3:10: fatal error: stdio.h: No such file or directory
 #include <stdio.h>

2. sysroot
GCC编译代码时,缺省是在目录/usr/include查找头文件,在目录/usr/lib查找库文件。如果是交叉编译,就不能在主机的目录下查找头文件和库文件,因为它们包含的是主机的应用程序的文件。我们需要指定目标单板的头文件和库文件。对于这种需求，GCC使用选项sysroot来实现。

GCC文档关于sysroot的描述如下：

--sysroot=dir
Use dir as the logical root directory for headers and libraries. For example, 
if the compiler normally searches for headers in /usr/include and libraries 
in /usr/lib, it instead searches dir/usr/include and dir/usr/lib.

If you use both this option and the -isysroot option, then the --sysroot option 
applies to libraries, but the -isysroot option applies to header files.

The GNU linker (beginning with version 2.16) has the necessary support for this 
option. If your linker does not support this option, the header file aspect of 
--sysroot still works, but the library aspect does not.

GCC文档关于sysroot的描述

3. 使用sysroot的编译
使用sysroot指定目录后，编译文件成功，没有任何问题。

aarch64-xilinx-linux-gcc --sysroot=/opt/petalinux/2019.2/sysroots/aarch64-xilinx-linux -c hello.c     -DPLATFORM_ZCU106 -std=c11 -o hello.o
aarch64-xilinx-linux-gcc --sysroot=/opt/petalinux/2019.2/sysroots/aarch64-xilinx-linux -o hello hello.o -Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed `pkg-config --cflags --libs glib-2.0 gstreamer-1.0 gstreamer-app-1.0` -lpthread -ldl -lrt -Wl,-rpath-link, -Wl,-O1 -Wl,--hash-style=gnu -Wl,--allow-multiple-definition

4. Makefile
在命令行下指定sysroot目录，只能适用于非常简单的代码。对于应用程序的开发，建议使用Makefile。下面提供一个Makefile的例子。

#source "$dir_build/environment-setup-aarch64-xilinx-linux"

PLNX_AARCH_PATH=/opt/petalinux/2019.2/sysroots/aarch64-xilinx-linux

WARNING_CFLAGS =  -Wall 

CC = aarch64-xilinx-linux-gcc --sysroot=$(PLNX_AARCH_PATH)

export PKG_CONFIG_PATH=$(PLNX_AARCH_PATH)/usr/lib/pkgconfig/
LDFLAGS += -lpthread -ldl -lrt -Wl,-rpath-link, -Wl,-O1 -Wl,--hash-style=gnu 

SOURCES = $(wildcard *.c)
OBJECTS = $(patsubst %.c,%.o,$(SOURCES))

CFLAGS = -DPLATFORM_ZCU106 -std=c11

all: hello

hello: hello.o
	$(CC) -o $@ hello.o $(LDFLAGS)

%.o: %.c
	$(CC) -c $< $(CFLAGS) -o $@

clean:
	rm -f $(wildcard *.o) hello

5. 得到sysroot和交叉编译器
在petalinux工程中，执行petalinux-build –sdk，编译完成后能得到sdk.sh。
安装sdk.sh，后得到文件environment-setup-aarch64-xilinx-linux。执行source environment-setup-aarch64-xilinx-linux，配置好交叉编译器的路径。
在Makefile里，设置sysroot为其中的sysroots/aarch64-xilinx-linux/,GCC就能找到正确的头文件和库文件。

hankf@xszgs4:/opt/petalinux/2019.2$ ls -l
total 28
-rw-r--r-- 1 root root  3502 Jan 17  2020 environment-setup-aarch64-xilinx-linux
-rw-r--r-- 1 root root 13970 Jan 17  2020 site-config-aarch64-xilinx-linux
drwxr-xr-x 4 root root  4096 Oct  5  2019 sysroots
-rw-r--r-- 1 root root    96 Jan 17  2020 version-aarch64-xilinx-linux
hankf@xszgs4:/opt/petalinux/2019.2$ ls -l sysroots/aarch64-xilinx-linux/
total 60
drwxr-xr-x  3 xilinx root 4096 Jan 13  2020 bin
drwxr-xr-x  2 xilinx root 4096 Jan 13  2020 boot
drwxr-xr-x  2 xilinx root 4096 Jan 13  2020 dev
drwxr-xr-x 46 xilinx root 4096 Jan 13  2020 etc
drwxr-xr-x  3 xilinx root 4096 Jan 13  2020 home
drwxr-xr-x  9 xilinx root 4096 Oct  5  2019 lib
drwxr-xr-x  2 xilinx root 4096 Jan 13  2020 media
drwxr-xr-x  2 xilinx root 4096 Jan 13  2020 mnt
dr-xr-xr-x  2 xilinx root 4096 Jan 13  2020 proc
drwxr-xr-x  2 xilinx root 4096 Jan 13  2020 run
drwxr-xr-x  3 xilinx root 4096 Jan 13  2020 sbin
dr-xr-xr-x  2 xilinx root 4096 Jan 13  2020 sys
drwxrwxrwt  2 xilinx root 4096 Jan 13  2020 tmp
drwxr-xr-x 10 xilinx root 4096 Oct  5  2019 usr
drwxr-xr-x  9 xilinx root 4096 Oct  5  2019 var
hankf@xszgs4:/opt/petalinux/2019.2$ source environment-setup-aarch64-xilinx-linux 
hankf@xszgs4:/opt/petalinux/2019.2$ aarch64-xilinx-linux-gcc --version
aarch64-xilinx-linux-gcc (GCC) 8.2.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
hankf@xszgs4:/opt/petalinux/2019.2$ which aarch64-xilinx-linux-gcc
/opt/petalinux/2019.2/sysroots/x86_64-petalinux-linux/usr/bin/aarch64-xilinx-linux/aarch64-xilinx-linux-gcc