Allocate class instances statically #191

jonathanperret · 2024-07-21T22:23:00Z

Issue

The classes that make up the AYAB firmware are currently dynamically allocated with new at the top level of main.cpp:

ayab-firmware/src/ayab/main.cpp

Lines 50 to 56 in e960ad4

    
           BeeperInterface    *GlobalBeeper::m_instance    = new Beeper(); 
        
           ComInterface       *GlobalCom::m_instance       = new Com(); 
        
           EncodersInterface  *GlobalEncoders::m_instance  = new Encoders(); 
        
           FsmInterface       *GlobalFsm::m_instance       = new Fsm(); 
        
           KnitterInterface   *GlobalKnitter::m_instance   = new Knitter(); 
        
           SolenoidsInterface *GlobalSolenoids::m_instance = new Solenoids(); 
        
           TesterInterface    *GlobalTester::m_instance    = new Tester();

Since these objects are allocated at the start of the program and never freed, there is no advantage to having them dynamically allocated. On the other hand, there are disadvantages:

dynamically allocated objects can use a few more bytes for the memory allocator's bookkeeping;
the memory used by these objects is not counted in the PlatformIO builder's statistics of RAM usage, that are printed after every build.

That last point in particular can hide the fact that the memory requirements for the firmware exceed the target microcontroller's RAM size (2048 bytes for the Atmega328p on an Arduino Uno).

Proposed solution

This PR replaces the use of new by the creation of statically allocated instances. The global pointers are then initialized to point to these instances.

Before this PR, here is what the output of the PlatformIO builder looks like:

RAM:   [======    ]  60.2% (used 1232 bytes from 2048 bytes)

Which looks reasonable. But after including the firmware's main objects in the statically allocated area as this PR does, here is the output:

RAM:   [========= ]  91.3% (used 1869 bytes from 2048 bytes)

Revealing that the memory actually available for the stack is much less than was suggested by the earlier output, causing issues like #190.

The memory saved here seems to fix #190 partially. At least, even with stack overflow detection enabled, the firmware can now survive reqInit and even knitting, from my quick test.

Note that this PR also deletes a series of uninitialized constant pointers that appear to have been remains from an earlier attempt at these global pointers.

Summary by CodeRabbit

New Features
- Improved instance management for key components by replacing dynamic memory allocation with stack-allocated instances, enhancing performance and reducing memory leak risks.
Refactor
- Streamlined the initialization process of singleton instances, resulting in clearer and more maintainable code.
Bug Fixes
- Addressed potential memory management issues by eliminating the use of new for singleton instances.

coderabbitai · 2024-07-21T22:23:07Z

Caution

Review failed

The pull request is closed.

Walkthrough

The recent changes in src/ayab/main.cpp involve a significant refactor of singleton instance management. Instead of using constexpr pointers to dynamically allocated instances, the code now utilizes stack-allocated instances, enhancing memory management safety and performance by eliminating potential memory leaks and overhead from heap allocations.

Changes

Files	Change Summary
`src/ayab/main.cpp`	Replaced `constexpr` pointers to singleton classes with direct stack-allocated instances.

Assessment against linked issues

Objective	Addressed	Explanation
Memory gets corrupted when processing serial messages (#190)	✅

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coderabbitai

Actionable comments posted: 0

Review details

Configuration used: CodeRabbit UI
Review profile: CHILL

Commits

Files that changed from the base of the PR and between e960ad4 and 9b1c3a8.

Files selected for processing (1)

src/ayab/main.cpp (1 hunks)

Additional comments not posted (2)

src/ayab/main.cpp (2)

39-45: LGTM! Improved memory management.

Replacing dynamic allocations with stack-allocated instances enhances memory management and performance.

47-53: LGTM! Correct initialization of static members.

The static members of the singleton classes are correctly initialized to point to stack instances.

Avoiding dynamic allocation saves some bookkeeping, but mainly it lets Platform.IO output a more faithful evaluation of the RAM requirements for the firmware.

coderabbitai bot reviewed Jul 21, 2024

View reviewed changes

jonathanperret mentioned this pull request Jul 22, 2024

com: shrink send/receive buffers from 256 to 64 bytes #193

Merged

X-sam approved these changes Jul 22, 2024

View reviewed changes

Allocate class instances statically

a212fc6

Avoiding dynamic allocation saves some bookkeeping, but mainly it lets Platform.IO output a more faithful evaluation of the RAM requirements for the firmware.

dl1com force-pushed the no-dynamic-alloc branch from 9b1c3a8 to a212fc6 Compare July 23, 2024 08:06

dl1com merged commit 9c8648f into AllYarnsAreBeautiful:v1.0-dev Jul 23, 2024
2 checks passed

jonathanperret deleted the no-dynamic-alloc branch July 23, 2024 16:06

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Allocate class instances statically #191

Allocate class instances statically #191

jonathanperret commented Jul 21, 2024 •

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	BeeperInterface *GlobalBeeper::m_instance = new Beeper();
	ComInterface *GlobalCom::m_instance = new Com();
	EncodersInterface *GlobalEncoders::m_instance = new Encoders();
	FsmInterface *GlobalFsm::m_instance = new Fsm();
	KnitterInterface *GlobalKnitter::m_instance = new Knitter();
	SolenoidsInterface *GlobalSolenoids::m_instance = new Solenoids();
	TesterInterface *GlobalTester::m_instance = new Tester();

Allocate class instances statically #191

Allocate class instances statically #191

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jonathanperret commented Jul 21, 2024 • edited by coderabbitai bot Loading

Issue

Proposed solution

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coderabbitai bot commented Jul 21, 2024 • edited Loading

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jonathanperret commented Jul 21, 2024 •

edited by coderabbitai bot

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