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QUESTION
I got an embedded project for cortex-m0+ and I would like to link with newlib-nano library. I'm learning, how things work (that you need to implement stubs for certain functions etc.). I've managed to create a working example which builds.
Source code:
...ANSWER
Answered 2022-Apr-08 at 09:12At https://github.com/32bitmicro/newlib-nano-1.0/blob/master/newlib/libc/stdio/printf.c iprintf
is an alias for printf
:
QUESTION
I am trying to work with flash memory on MPC5748G - a microcontroller from NXP running FreeRTOS 10.0.1, and I get some behaviour that I can't understand.
I am allocating memory manually, and the assignment seems not to work. However, I can reach the value at the address when using 'printf' - but only from the same function. (I'm using the copy of a pointer, to make sure that some sore of compiler optimisation doesn't take place)
...ANSWER
Answered 2022-Feb-16 at 16:50The problem was writing to FLASH memory - it hasn't been correctly initialized.
The proper way to write to flash on MPC5748g using the SDK 3.0.3 is following:
- save flash controller cache
- initialise flash
- check and protect UT block
- unblock an address space
- erase a block in this space
- check if the space block is blank
- program the block
- verify if the block is programmed correctly
- check sum of the programmed data
- restore flash controller cache
The strange behaviour of printf and pointer was due to compiler optimization. After changing the compiler flags to -O0 (no optimization), the error was consistent.
The same consistent error can be achieved when marking the pointers as 'volatile'.
QUESTION
I´m having troubles understand a compiler warning that we have in our code. The code we have are similar to the one in this example that give the warning (-Wchar-subscripts). We are using ARM gcc 9.2.1 embedded and newlib as standard library.
...ANSWER
Answered 2022-Jan-26 at 12:22This appears to be the very same bug as discussed in Bugzilla here Bug 95177 - error: array subscript has type char. Basically gcc is inconsistent in its diagnostics and this behavior only appeared in later versions.
As discussed in that thread, passing char
to the ctype.h functions could in theory be a problem in case the char
would contain anything unknown. These functions are defined as expecting the input to be something representable as unsigned char
, see C17 7.4:
In all cases the argument is an int, the value of which shall be representable as an unsigned char or shall equal the value of the macro EOF
Therefore int i = isspace((unsigned char)str[1]);
makes the warning go away.
But the warning is as you can tell inconsistent. Which could possibly be explained by when you are using ctype.h, the compiler could sometimes be picking a macro and sometimes a function.
Just disable it and regard it as a false positive. According to the Bugzilla log above, this should now have been fixed very recently. gcc (trunk) and gcc >10.3 doesn't give this warning any longer.
QUESTION
I've got some software compiled to run on an embedded NRF24 target, using a gcc-arm-none-eabi toolchain from here (a custom one that provides gdb with support for python3) . I'm trying essentially, malloc
an array from the GDB debugger console at runtime, then fill it with elements that I provide.
I have a pointer defined in a .c file like: static float32_t *array;
.
I want to then call a cmd like: call (void*) malloc(num_of_elements*sizeof(float32_t))
from inside the GDB console to allocate an array at runtime, and then fill it with elements with something like maybe: call (void*) memcpy(array, {var1, var2... var n}, n)
My issue is the GDB debugger cannot find the malloc
stdlib function. If I do something like:
ANSWER
Answered 2021-Dec-15 at 02:01It can't find this function
The function may not be linked into your binary.
- Does your binary call
malloc
elsewhere? - Do you link against
libc.so
orlibc.a
? - Does
nm a.out | grep ' malloc'
find it?
it is fine with finding fns, like
memcpy
If your binary calls memcpy
and you link against libc.a
, then memcpy
implementation will be linked in. Using the same nm
command from above will show that the memcpy
symbol is present and malloc
is not.
If you want to call malloc
at runtime, you need to make sure it's linked in. One way to achieve this is to add:
QUESTION
Often a question leads me into another question.
While trying to debug an inline assembly code, I met with another basic problem.
To make long story short, I want to run arm64 baremetal hello world program on qemu.
ANSWER
Answered 2021-Dec-10 at 11:05When you build a program for "bare metal" that means that you need to configure your toolchain to produce a binary that works on the specific piece of bare metal that you try to run it on. For instance, the binary must:
- put its code somewhere in the machine's memory map where there is either ROM or RAM
- put its data where there is RAM
- make sure that on startup the stack pointer is correctly initialized to point into RAM
- if it wants to print output, include routines which access a suitable device on that machine. This is likely a serial port, and serial ports are often entirely different devices, located at different addresses, on different machines
If any of these things are wrong or don't match the actual machine you run on, the result is typically exactly what you see -- the program crashes without output.
More specifically, rdimon.specs tells the compiler to build in C library functions which do some of this via the "semihosting" debugger ABI (which has support for "print string" and some other things). Your QEMU command line doesn't enable implementation of semihosting (you can turn it on with the -semihosting option), so that won't work at all. But there are probably other problems you're also hitting.
QUESTION
I am trying to build a 64-bit executable RISC-V ELF using the RISC-V toolchain with newlib and a linker script that places the text section at 0x100 and the data section starting at 0x100000000 (greater than the 2 GB limit). However, I get the following error:
...ANSWER
Answered 2021-Dec-04 at 23:55There are similar situations on other 64-bit platforms such as x86-64 and ARM64.
The normal way to load a static address is as a 32-bit immediate, either absolute or pc-relative. This is more efficient than requiring 64-bit immediates every time an address is used, which tend to need a longer and slower sequence of instructions. But it does mean that all static code and data needs to fit in 2 GB.
You can use much more of the 64-bit address space for dynamically allocated objects, since they don't need their addresses coded into the binary. This limit is only for static code and data. Also, I'm not sure about RISC-V, but I believe on other platforms, the 2 GB limit applies separately to each shared library, so a really huge application could still be written by breaking off pieces into shared libraries.
On x86-64 and ARM64, GCC does support a "large" code model in which all static addresses are loaded as 64-bit, with the corresponding performance penalty. It looks like this is not currently supported for RISC-V.
QUESTION
Im trying to check if an item exists in my dynamodb table using the code below: I want to be able to run something once I can retrieve the item. The partition key is envName and the sort key is configurationName
...ANSWER
Answered 2021-Sep-10 at 19:09You have to supply the key attribute(s), with the correct type(s), when calling GetItem.
You've included non-key attributes (status
). When you supply non-key attributes, your GetItem request will fail with a ValidationException including this error message:
QUESTION
I feel like this question has been asked a bunch of times, but none of the answers I have found seem to be working for me. I'm extremely new to CMake and C/C++ as I come from the world of Java, and am struggling to understand cmake and how it works.
Anyways, basically I have the folder structure below. This is an esp-idf project, so I don't know if that has anything to do with what I'm running into.
...ANSWER
Answered 2021-Jul-09 at 13:46The ESP-IDF build system is built on top of CMake. This means you can use all the standard features of CMake in your files. However, the the ESP-IDF system predefines many functions, and makes many assumptions about the layout of your project, supposedly to make things "easier". Instead of reading CMake documentation, start by reading and understanding the ESP-IDF build system documentation:
https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/build-system.html
It looks to me like there is a particular layout expected for subcomponents, including the format of the CMakeLists.txt
file. Specifically, move Metriful
under a new directory called components
, or add Metriful
to EXTRA_COMPONENT_DIRS
near the top of your root CMakeLists.txt
If Metriful is not written as an esp-idf component, this may not work. However, the document also describes how to link to "pure CMake" components, which will look something like this (at the end of your root CMakeLists.txt
).
QUESTION
I was trying setup enviorment to develop some program for new PICO, but only compile one time, after I haved this error:
...ANSWER
Answered 2021-Feb-22 at 13:50Okey, solution was erease the content from autogenerated file, save file and build again...,
After several builds error appear again, and same procedure was success :D
Thanks all that tried to helped me if knows about root issue will be great!
QUESTION
Update: Writing this out allowed me to spot where I was going wrong, but not why. I am obviously calling fgets in the wrong way, because after five calls I get to the address 0x221000 which is where the mmapped memory is - I am writing at higher addresses - but I don't know why that that is happening. Could someone explain?
This is a bit complex and I'm at a loss to see why this behaviour is seen: I don't know if I have got the basics wrong or if it's a feature of Spike/PK.
To note: the libc here is provided by newlib and the code is compiled as riscv64-unknown-elf.
Short version I have input code written in RISC-V assembly that previously ran smoothly, but since I introduced a system call to mmap it crashes the fifth time it is executed. Is the problem because I have got the wrong sequence of calls or possibly an issue with the Spike emulator and PK proxy kernel?
Long explanation
I am writing a Forth-like threaded interpreted language. It is currently targeted at the PK proxy kernel on the Spike emulator, but hopefully soon to run on 'real' hardware. The code is at https://github.com/mcmenaminadrian/riscyforth
The TIL implements an endless loop to pick up input calling, in sequence, a routine to get the filepointer for standard input and then a routine to get the input.
To get the standard input filepointer (which is stored on the stack):
...ANSWER
Answered 2021-Apr-20 at 07:11By repeatedly opening the file my code was eating up more and more memory and eventually overwrote part of the memory range allocated via mmap. I solved this by storing the value of the file pointer in the .bss (inputfileptr) and only opening it once:
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