Resulting binaries: Exactly same code produces very different resulting binaries (IDFGH-6323)

[carlessole]

• Module or chip used: ESP32-WROVER (With ESP_PROG)
• IDF version: v4.3.1
• Build System: CMake/idf.py (usingEclipse Plugin)
• Compiler version: esp-2020r3-8.4.0
• Operating System: Windows
• (Windows only) environment type: -.
• Using an IDE?: Yes. Eclipse + ESP-IDF plugin, but also thorugh CLI
• Power Supply: USB

Hi everyone,
I have noticed a behaviour that it is not what I thought it was correct.

When I compile multiple times exactly the same source code. The resulting binaries:

1. Sometimes are almost the same, in exception of the compile date/time and some final CRC. That is the behaviour that I expect.
2. Sometimes the resulting binaries are very very different even the size is not the same (just few bytes). That is the behaviour that I don't understand. Is that correct? Why is happening?

I was expecting always the 1st case because then it is easier to probe that both binaries have been created from the same source code.

Here I attach some images when compilation differs a lot:

[negativekelvin]

esp-idf/Kconfig

Lines 204 to 209 in 9919b75

	config APP_REPRODUCIBLE_BUILD
	bool "Enable reproducible build"
	default n
	select COMPILER_HIDE_PATHS_MACROS
	help
	If enabled, all date, time, and path information would be eliminated.

[igrr]

Linking #5251 and #5873.

I think in 4.3 this might be a regression in the linker script generator, where on different runs it may produce different order of libraries. This should be fixed in 404ee09, will be part of the next v4.3.2 bugfix release.

Additionally in release/v4.4 there is a new option CONFIG_APP_REPRODUCIBLE_BUILD which @negativekelvin has kindly linked above, it will also make ELF files identical across builds, so event the ELF SHA256 value in binary image header will be stable.

[carlessole]

Thanks @igrr amd @negativekelvin ,

@negativekelvin : I'm using v4.3.1 and so I have not that config field avialble. Moreover I'm ok that few things as paths, and date/time differs. But I see so many changes apart from these ones

@igrr : I think that my problem is probably related with the linker issue. I will try when v4.3.2 comes out to test it.

Thanks

[igrr]

@carlessole v4.3.2 has been released, please give it a try and see if this issue is fixed for you.

[Alvin1Zhang]

@carlessole Thanks for reporting, would you please help a try with the newly released IDF v4.3.2 and share any updates? Thanks.

[Alvin1Zhang]

@carlessole Thanks for reporting, will close due to short of feedback, feel free to reopen with more updates. Thanks.