Compile not optimized Libgcc for ARM - gcc

Good morning,
I need to compile libgcc from scratch without deploying the ARM optimized version which is defined in ieee754-sf.s in the ARM back-end.
Does anyone knows how to configure GCC for excluding ieee754-sf.s ( in libgcc/config/arm ) to compile from scratch libgcc, in particular compiling vanilla floating-point soft-fp emulation which is in libgcc/spft-fp ?
Thanks

I dont know a configure command which does what you want. However if you want to do these modifications, you will need to modify lib1funcs.S to delete the references to the two files. you will need also to modify the t files (t-elf and t-arm at least) . gcc/config/arm/elf.h sould probably be modified too.
You can take a look at microblaze config directory. it shows a minimalist example

Related

Compile single static library for Cortex M3, M4, M23 and M33

I'm currently working on a rather generic communication stack. It gets bytes in on one end, parses the packet and calls a callback.
I want to have this stack in a static library (i.e. libcommstack.a).
The library is aimed towards embedded ARM Cortex-M devices. At the moment we have specified that at least a Cortex-M3 should be used (but it should also work for an M4 or M33).
Right now I'm integrating it into another application to verify that linking it is possible. In the future the idea is that we will ship this .a file to customers so they can build their application around it, without having direct access to our sources (to encapsulate our IP).
We are using GCC ARM v7.2.1 to compile both the library and the application that is linked to it.
The application I'm trying to integrate it with is compiled for a Cortex M33 with -mfloat-abi=hard -mfpu-fpv6-sp-d16.
The code for the library does not use any floating points and is compiled using -march=archv7-m (both have the -mthumb flag).
Linking seemed to all go well, until I actually called a function from the lib. At that point the linker starts to complain:
application.elf uses VFP register arguments, libcommstack.a(somefile.c.obj) does not
failed to merge target specific data of file libcommstack.a(somefile.c.obj)
Since I'm not using floating points in the library and I don't know (upfront) if the target application does or does not have an FPU (or even uses floats), I'm not sure how to approach this.
I figured there would be two approaches:
Compile a single version of the lib, using an instruction set that all of the microcontrollers understand. I was hoping that this would be the case with ARMv7 (although I'm not yet 100% confident that the M23/M33 also support this).
Compile a lot of different libs for the different flavors based on the different architectures, FPU, etc.
As you can imagine, I would prefer to keep it simple and go for option 1, but I'm not sure how to "convince" the linker to link these two (or perhaps how to convince the compiler NOT to care about floating points for the lib).
Does anyone know if option 1 is feasible and how it can be achieved?
If it is not feasible, what would be the variables to keep in mind to determine the different build flavors?
Does anyone know if option 1 is feasible
Well, feasible, probably.
how it can be achieved?
Get all the processors you want to support and determine the instructions sets available on all these processors. Then compile for that instruction set.
But, please don't, that is a workaround.
If it is not feasible, what would be the variables to keep in mind to determine the different build flavors?
Gcc has something like "multilib profiles". See arm-none-eabi-gcc --print-multi-lib output. If you have newlib installed, you can go to /usr/arm-none-eabi/lib/thumb/ and see the directories there - newlib is compiled for each profile and installs separate library for it and different library is picked up depending on configuration. Compile for each of those profiles, and package your library by putting libraries in proper /usr/arm-none-eabi/lib/proper/directory/here and compiler will pick them up by itself (see gcc -v output for library search paths). For an example search newlib sources where it happens, can't find it. (Here's my example). With cmake as a backend as a example you could compile and install as follows:
arm-none-eabi-gcc --print-multi-lib |
while IFS=';' read -r dir opts; do
cmake -B builddir CMAKE_C_FLAGS="$opts" CMAKE_INSTALL_LIBDIR="$dir"
cmake --build builddir
cmake --install builddir --prefix "/usr/arm-none-eabi/"
done

Library doesn't properly link at command 'make'

I am trying to use some open-source CFD code, and it uses PETSC and some other libraries, so I installed them. But when I try to compile program useing 'make', it seems like libraries are not properly linked with makefile
It seems like petsc isn't properly linked, but I can't know why...
The problem is that PETSc depends on some more libraries (X11) than the CFD package counted on. It should have a proper configure that figures these out. However, you can get the link line you need using
cd PETSC_DIR; make getlinklibs
which you can then put in LIBFLAG.

how to manually include .config when compiling external kernel module?

I'm afraid my question is a bit complex. Appreciate anyone who can help.
Some background:
I have a 3rd party SW package that compile both kernel modules and user space applications.
Unfortunately, this 3rd party is very complex, and doesn't use Kbuild for building kernel modules (I tried without success)
When compiling the kernel modules, I add -I{path to kernel headers}, but I see the .config file is not being parsed in the compilation, which, of course, causes many errors.
I tried to manually add all flags from .config to gcc in command line (using a script to generate the command line) but that was a very very long line and gcc couldn't handle it.
So my question would be: Is there a way to force all these flags to gcc somehow?
Appreciate your ideas :)
Clarification:
The 3rd party SW can compile on older kernels (2.6, 2.4) I'm trying to compile it for 3.2
Maybe if someone can explain how the original kernel Makefile manages the .config file, I can mimic that behavior.
After digging in the kernel sources, I found the answer. Here it is in case someone needs it.
There's an automatically generated h file called autoconf.h which contains all the relevant definitions in C pre processor format. Just need to include it manually when compiling the module.
Also in theory, I could use my script to create such a file and include it from the sources.
Hope this helps someone. Now on to the next problem :)

Referencing Source Files of Shared Libraries in Valgrind

We have a software project which has the primary purpose of providing a library and API. We also provide example programs and utilities that use this library.
So, let's say that I have built and installed our library. When I run valgrind on one of the example / utility programs, I obviously see references to functions in the library. The issue is that it doesn't provide line numbers, and I would like it to.
Is there a way to tell Valgrind to reference source files that aren't obviously part of an executable, but are part of the source code for a library that is linked-in to the executable?
Thanks!
Make sure that you are compiling shared library with -g to add debug information. This should be enough for Valgrind to reference source files. See http://valgrind.org/docs/manual/faq.html#faq.unhelpful for more information.

Migrating from Winarm to Yagarto

This question must apply to so few people...
I am busy mrigrating my ARM C project from Winarm GCC 4.1.2 to Yagarto GCC 4.3.3.
I did not expect any differences and both compile my project happily using the same makefile and .ld files.
However while the Winarm version runs the Yagarto version doesn't. The processor is an Atmel AT91SAM7S.
Any ideas on where to look would be most welcome. i am thinking that my assumption that a makefile is a makefile is incorrect or that the .ld file for Winarm is not applicable to Yagarto.
Since they are both GCC toolchains and presumably use the same linker they must surely be compatable.
TIA
Ends.
I agree that the gcc's and the other binaries (ld) should be the same or close enough for you not to notice the differences. but the startup code whether it is your or theirs, and the C library can make a big difference. Enough to make the difference between success and failure when trying to use the same source and linker script. Now if this is 100% your code, no libraries or any other files being used from WinARM or Yagarto then this doesnt make much sense. 3.x.x to 4.x.x yes I had to re-spin my linker scripts, but 4.1.x to 4.3.x I dont remember having problems there.
It could also be a subtle difference in compiler behavior: code generation does change from gcc release to gcc release, and if your code contains pieces which are implementation-dependent for their semantics, it might well bite you in this way. Memory layouts of data might change, for example, and code that accidentally relied on it would break.
Seen that happen a lot of times.
Try it with different optimization options in the compile and see if that makes a difference.
Both WinARM and YAGARTO are based on gcc and should treat ld files equally. Also both are using gnu make utility - make files will be processed the same way. You can compare the two toolchains here and here.
If you are running your project with an OCD, then there is a difference between the implementation of the OpenOCD debugger. Also the commands sent to the debugger to configure it could be different.
If you are producing an hex file, then this could be different as the two toolchains are not using the same version of newlib library.
In order to be on the safe side, make sure that in both cases the correct binutils are first in the path.
If I were you I'd check the compilation/linker flags - specifically the defaults. It is very common for different toolchains to have different default ABIs or FP conventions. It might even be compiling using an instruction set extension that isn't supported by your CPU.

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