https://github.com/github0null/sdcc-binutils-mcs51
use sdcc+as+ld to build your mcs51 project
https://github.com/github0null/sdcc-binutils-mcs51
8051 8052 as binutils ld mcs51 sdcc
Last synced: 6 months ago
JSON representation
use sdcc+as+ld to build your mcs51 project
- Host: GitHub
- URL: https://github.com/github0null/sdcc-binutils-mcs51
- Owner: github0null
- Created: 2025-08-26T04:42:59.000Z (6 months ago)
- Default Branch: master
- Last Pushed: 2025-08-26T09:55:54.000Z (6 months ago)
- Last Synced: 2025-08-26T11:22:14.393Z (6 months ago)
- Topics: 8051, 8052, as, binutils, ld, mcs51, sdcc
- Language: Shell
- Homepage:
- Size: 89.8 KB
- Stars: 0
- Watchers: 0
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
[中文](./README_zh.md)
# Summary
This is the [sdcc](https://sdcc.sourceforge.net/) + [binutils](https://www.gnu.org/software/binutils/) compiler suite prepared for mcs51.
It uses sdcc as the front end to generate assembly and then uses gnu as+ld to complete the compilation and linking.
The source code of this repository is referenced from: https://github.com/volumit/sdcc_aurix_scr_42
**What's the difference ?**
The linker of sdcc does not support the dead code elimination function (i.e., deleting unused functions in the program), so when compiling a large number of c files with sdcc, the generated hex will be very large in size.
This solution can solve this problem.
binutils as supports syntax like `.section.text._func`, so a section can be generated for each function. Thus, the ld can use the `--gc-sections` feature to remove unused sections.
This toolchain is in the experimental stage, it has already passed the test suite.
# Notice
Some functions may be somewhat different from sdcc.
- **Not support overlay**：All local variables are saved to the stack, so the `--stack-auto --nooverlay` parameter must be enabled,otherwise, the compilation will fail.
- **Not support medium, huge model**：Only the 'small' and 'large' models are supported
- **Not support address > 64K**：References to addresses greater than '0xFFFF' are not supported, and thus SFR32 is not supported either
- **Not support xstack**: The stack can only be located in 'iram'
- **Absolute address position**：'__at(xxx)' cannot be used for absolute address localization of 'data idata xdata code', ** except for the SFR register **, because ld uses linker script for address allocation. To use this function, refer to the "Usage" section below, or directly define the absolute position of the symbol using '-Wl,--defsym='
- **Stack**：Since the overlay feature is not supported, all local variables and function parameters are stored in the stack. This poses a challenge for mcs51 because even with the large model, the maximum remaining size of the stack is' 256-32 = 224 bytes'. Therefore, for function calls, Don't use too many function parameters and nested calls, as this will accelerate stack overflow.
# Build It
Run `apt install build-essential` to install gcc at first.
Then, run:
```shell
git clone https://github.com/github0null/sdcc-binutils-mcs51.git
cd sdcc-binutils-mcs51
git submodule update --init --recursive
cd build
./do_all
```
After compilation is completed, the generated binary is located in: `build/_install`
## Build It For win32
Please install `x86_64-w64-mingw32-gcc` and `libz-mingw-w64-dev` first.
cd to build-win32 and run:
```shell
./binutils_configure
./binutils_make
./sdcc_configure
./sdcc_make
```
# Usage
Please refer to the Makefile in the `examples` directory
```makefile
main.hex: main.o delay.o foo.o
@echo "link $@"
$(CC) -mmcs51 --model-small --stack-auto --nooverlay --out-fmt-ihx -Wl,--print-memory-usage -o $@ $^
%.o: %.c | Makefile
@echo "CC $<"
@$(CC) -c -mmcs51 --model-small --stack-auto --nooverlay -o $@ $<
```
## Absolute address reference
If you want to use an absolute address reference for 'data idata xdata code', please implement it by referring to the following snippet:
```c
extern __xdata unsigned char REG_1_RES; // 0xCA00
extern __xdata unsigned char REG_2; // 0xCA01
void dummy()
{
__asm
.globl _REG_1_RES, _REG_2
.section .xdata, "aw"
.equ _REG_1_RES, 0xCA00
.equ _REG_2, 0xCA01
__endasm;
}
```
Another more convenient method is to directly pass the compilation parameters `-Wl,--defsym=_REG_1_RES=0xCA00 -Wl,--defsym=_REG_2=0xCA01` to directly define the absolute position of the symbol.
And then define a declaration in you code:
```c
extern __xdata unsigned char REG_1_RES;
extern __xdata unsigned char REG_2;
```
> Note: SDCC will add a '_' prefix for the symbol