问题
I do not know much about cross-comping. I am using eclipse on linux machine to cross compile armv7-a Hellow world Example.
#include <iostream>
using namespace std;
int main() {
cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!!
return 0;
}
cross settings : arm-none-eabi-
path : /usr/lib/arm-none-eabi
cross g++ compiler :g++ -c -fmessage-length=0 -mcpu=cortex-m3 -march=armv7-a
I got the following linker error :
13:54:47 **** Incremental Build of configuration Debug for project Hellocpp ****
make all
Building file: ../src/main.cpp
Invoking: Cross G++ Compiler
arm-none-eabi-g++ -O0 -g3 -Wall -c -fmessage-length=0 -mthumb -mcpu=cortex-m3 -march=armv7-a -MMD -MP -MF"src/main.d" -MT"src/main.o" -o "src/main.o" "../src/main.cpp"
../src/main.cpp:1:0: warning: switch -mcpu=cortex-m3 conflicts with -march=armv7-a switch
//============================================================================
Finished building: ../src/main.cpp
Building target: Hellocpp
Invoking: Cross G++ Linker
arm-none-eabi-g++ -o "Hellocpp" ./src/main.o
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libstdc++.a(locale_init.o): In function `(anonymous namespace)::get_locale_mutex()':
/build/libstdc++-arm-none-eabi-yOFevq/libstdc++-arm-none-eabi-10/build/libstdc++/src/c++98/../../../../src/libstdc++-v3/src/c++98/locale_init.cc:66: undefined reference to `__sync_synchronize'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libstdc++.a(locale.o): In function `get_locale_cache_mutex':
/build/libstdc++-arm-none-eabi-yOFevq/libstdc++-arm-none-eabi-10/build/libstdc++/src/c++98/../../../../src/libstdc++-v3/src/c++98/locale.cc:36: undefined reference to `__sync_synchronize'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libstdc++.a(future.o): In function `__future_category_instance':
/build/libstdc++-arm-none-eabi-yOFevq/libstdc++-arm-none-eabi-10/build/libstdc++/src/c++11/../../../../src/libstdc++-v3/src/c++11/future.cc:64: undefined reference to `__sync_synchronize'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-abort.o): In function `abort':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/stdlib/../../../../../newlib/libc/stdlib/abort.c:63: undefined reference to `_exit'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-exit.o): In function `exit':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/stdlib/../../../../../newlib/libc/stdlib/exit.c:70: undefined reference to `_exit'
makefile:45: recipe for target 'Hellocpp' failed
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-fstatr.o): In function `_fstat_r':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/fstatr.c:62: undefined reference to `_fstat'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-openr.o): In function `_open_r':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/openr.c:59: undefined reference to `_open'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-sbrkr.o): In function `_sbrk_r':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/sbrkr.c:58: undefined reference to `_sbrk'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-signalr.o): In function `_kill_r':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/signalr.c:61: undefined reference to `_kill'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-signalr.o): In function `_getpid_r':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/signalr.c:97: undefined reference to `_getpid'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-writer.o): In function `_write_r':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/writer.c:58: undefined reference to `_write'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-closer.o): In function `_close_r':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/closer.c:53: undefined reference to `_close'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-isattyr.o): In function `_isatty_r':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/isattyr.c:58: undefined reference to `_isatty'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-lseekr.o): In function `_lseek_r':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/lseekr.c:58: undefined reference to `_lseek'
/usr/lib/gcc/arm-none-eabi/6.3.1/../../../arm-none-eabi/lib/libc.a(lib_a-readr.o): In function `_read_r':
/build/newlib-jo3xW1/newlib-2.4.0.20160527/build/arm-none-eabi/newlib/libc/reent/../../../../../newlib/libc/reent/readr.c:58: undefined reference to `_read'
collect2: error: ld returned 1 exit status
make: *** [Hellocpp] Error 1
"make all" terminated with exit code 2. Build might be incomplete.
How can I solve this ?
回答1:
These functions are generally part of libgloss for embedded targets.
If you don't want to provide your own versions of these functions, you can use --specs=nosys.specs. By using this spec ( you can read it, it is a text file), you will tell the compiler to change link spec and link against nosys libgloss which contains default versions of these functions.
Be careful you will need to link with --specs=nosys.specs -mthumb -mcpu=cortex-m3 -march=armv7-m or at least with the mcpu option otherwise you will have undefined reference to __sync_synchronize.
回答2:
It is important that the cross compiler and its settings fit the target setup where the application will be run. There is not enough information given here, but:
- arm-none-eabi is for bare-metal systems, i.e. no operating system is
involved or you are just compiling one. This means that the
environment may not provide the resources for the import
<iostream>. There is just nothing to<cout>to and you have to resort to the functionality base provided by the hardware vendor (e.g. writing your helloworld into a UART). If you are really developing such a system, it would be recommendable to use the provided hello world (or blinky) examples. - If you are running linux-based system arm-linux-gnueabi or arm-elf may work
- a cortex-m3 runs on
march=armv7-m
来源：https://stackoverflow.com/questions/64834134/linking-fail-for-arm-cross-compiler