I am trying to convert .c files for ARM (ARMv7l for Raspberry Pi2) but I could not find any online converter or understand how it works. Previously these .c files were executable in Windows platform and thus unable to execute on Pi's arm architecture. Does anybody can assist me in this?
Any c compiler can generate assembly code from C code, if your objective is specifically to generate assembly code for arm then you'll need a cross compiler such as the GNU arm embedded toolchain.
For gcc on particular you just need to use the -S option when compiling, so the line looks something like:
gcc -S -source.c -o output.s
Of course you'll need to include any headers and include directories for it to compile.
if you simply want to cross compile it, then simply do the full compilation assemblage and linking process. Depending on how low level the c code is it's actually possible for it not to work on the pi 2 (but it will compile)
Related
I am following the tutorial at https://littleosbook.github.io/ and wanted to understand whether or not what I have currently working is conceptually correct. In terms of where I am at, I am using macOS 10.15.7 for the development and was able to call a C function from the loader. The loader is in assembly. However, I used the Clang compiler (Apple clang version 12.0.0) to compile the C file in which the aforementioned C function is. Then, I compiled the C file to generate an object file and linked the .o file with loader.o
Is this how it should be done? Or should I be trying to firstly install gcc or clang inside the OS and have that compiler compile the C function for me?
I need to use the GSL library in my program on LPCXpresso 4367(ARM CORTEX M4). I tried to follow the library linking procedure for LPC xpresso but the MCU linker is giving me these errors:
MCUXpressoIDE_10.3.0_2200\workspace\test1\Debug/../src/test1.c:53: undefined reference to 'gsl_linalg_LU_decomp'
MCUXpressoIDE_10.3.0_2200\workspace\test1\Debug/../src/test1.c:56: undefined reference to 'gsl_matrix_alloc'
MCUXpressoIDE_10.3.0_2200\workspace\test1\Debug/../src/test1.c:57: undefined reference to 'gsl_linalg_LU_invert'
and so on for other functions as well.
I have the libgsl.a and libgslcblas.a precompiled libraries for windows which works perfectly on codeblocks on windows with GCC compiler.
I read that I need to crosscompile library for the arm-none-eabi-gcc toolchain. But can someone please provide me the procedure as well?
the libgsl.a and libgslcblas.a precompiled libraries for windows
Those won't do for ARM.
In order to work on another platform, these libs need to be compiled from source code with the proper compiler (and settings - Cortex-M4F requires Thumb2 instruction set).
As the libraries are precompiled for Windows they don't work for ARM (as it is said in the other answer)
You need to cross compile the libraries first. If you install the GSL libraries following this procedure, you only need to change the parameters in the ./config according to your platform, for example I used:
./config --host=arm-linux-gnueabihf --prefix=/home/yourname/gsl_arm
Inside the .zip file with the gsl-2.5 files, there is a file called INSTALL. There you can find more details on the options for cross compiling.
Make sure to make clean before if you have already compiled the library for different settings. After cross-compiling the library when you run make check on the terminal you will probably get errors, but still it works. Continue with make install and you are ready to use it.
I built a bunch of simple C programs for school on my Mac (OSX). I had compiled all of the programs and tested them all on my Mac with a Makefile. Everything worked well.
To prep for an assignment tomorrow, I decided to transfer all of these files (compiled and source code) via SSH to the class network (OS is Ubuntu). I wanted to make sure everything worked as expected there.
Once I transferred everything, when I tried to use the Emacs shell to run the compiled programs, I got a Cannot execute binary file error. Then, once I recompiled via my Makefile over SSH on the Ubuntu machine, it worked fine. But why not before?
I know this is obvious to some of you, but I don't know why a compiled C program will run fine on my machine, but then have to be recompiled on a different machine even with the operating systems being different?
Here is an example of my Makefile compile commands:
example: example.c
gcc -Wall -pedantic -ansi example.c -o example
I'm pretty new to C (obviously). This question, Why does my program run on Ubuntu gcc but not OSX gcc?, seems similar but I don't understand the answer.
Like other have mentioned the C code might be compatible but Linux and OSX use different binary formats which are not compatible. Thus you will need to recompile to make your code run on the other platform.
Linux uses a binary format called ELF
OSX uses a binary format called Mach-O
See Is a Linux executable “compatible” with OS X? for a more in depth explanation.
so to add to Marius's very good explanation:
they actually use the same x86-64 (amd64) calling convention (ABI) so they are compatible on another level, deeper than just C... but they are packaged in different object file formats (as described by Marius).
The other major difference is the linker... so while they both implement std C functions, they are in different libraries so if they are dynamically linked the symbols are in the wrong place.
I am trying to build a gcc cross compiler. I understand that before compiling the cross compiler I need to have the target binutils built already. why the building of the compiler need the target binutils ? the compiler alone only takes high level code and turn it to the assembly that I defined it in the compiler sources. so why do I need the target bintools for compiling the cross compiler ? It is written in all of the cross compiler documentation that I need them to be build before compiling the cross compiler. (e.g. http://wiki.osdev.org/Building_GCC and http://www.ifp.illinois.edu/~nakazato/tips/xgcc.html).
GCC needs an assembler to transform the assembly it generates into object files (machine code), and a linker to link object files together to produce executables and shared libraries. It also needs an archiver to produce static libraries/archives.
Those three are usually provided by the binutils package (among other useful tools): the GNU assembler as, linker ld and the ar archiver.
Your key question seems to be:
why the building of the compiler need the target binutils ?
As described in Building a cross compiler, part of the build process for a GNU cross-compiler is to build runtime libraries for the target using the newly-compiled cross-compiler. So the binutils for the target need to be present for that step to succeed.
It may be possible to build the cross-compiler first, using empty files for the subset of binutils components that gcc needs - such as as and ld and ar and ranlib - then build and install the target binutils components into the proper locations, then build the target runtime libraries.
But it would be less error-prone to do things the following way (and the documentation recommends this): build binutils for the target first, place the specified executables in gcc's source tree, then build the cross-compiler.
The binutils (binary utilities) provide low-level handling of
binary files, such as linking, assembling, and parsing ELF files. The GCC
compiler depends on these tools to create an executable, because it generates
object files that binutils assemble into an executable image.
ELF is the format that Linux uses for binary executable
files. The GCC compiler relies on binutils to provide much of the platform-specific functionality.
Here your are cross-compiling for some other architecture not for x86. So resulting binutils are platform-specific
while configuring has to give --host!=target. i.e --host=i686-pc-linux-gnu
where --target=arm-none-linux-gnueabi.
So resulting executable are not same which host already having binutils.
addition
the basic things needs to be known.
The build machine, where the toolchain is built.
The host machine, where the toolchain will be executed.
The target machine, where the binaries created by the
toolchain are executed.
So binutils will be having tools to generate and manipulate binaries
for a given CPU architecture. Not for the one host is using
I understand that compilers convert c source code to assembly and then to machine code. I searched through every compiler setting I could find, and their website but I can't get it to generate assembly. Also, the website states that Dev-C++ uses AT&T assembly, can I also convert from that to Intel?
Dev-C++ seems to use GCC.
You can try this option: gcc -S -masm=intel as answered in this question: How do you use gcc to generate assembly code in Intel syntax?
I do not know how to set command line options on Dev-C++ but guides can be easily found.
C:\Program Files (x86)\Dev-Cpp\MinGW32\bin>gcc -S -masm=intel try.cpp
Type this in command prompt(location of gcc depends on where you have install dev-C++),it will generate assembly file,in my case try.s