Memory allocation in Blockchain / Solidity - Step-by-Step Execution

Concept Flow - Memory allocation

Start Transaction

↓

Request Memory Allocation

↓

Check Available Memory

Yes No↓

Allocate Memory

↓

Use Memory

↓

Free Memory

↓

End Transaction

This flow shows how memory is requested, checked, allocated, used, and freed during a blockchain transaction.

Execution Sample

Blockchain / Solidity

memoryPool = 1000
request = 300
if request <= memoryPool:
    memoryPool -= request
    # use memory
    memoryPool += request

This code simulates allocating and freeing memory from a pool during a blockchain operation.

Execution Table

Step	memoryPool Before	request	Condition (request <= memoryPool)	Action	memoryPool After
1	1000	300	True	Allocate 300 memory	700
2	700	300	N/A	Use memory (no change)	700
3	700	300	N/A	Free 300 memory	1000
4	1000	1100	False	Throw Error: Out of Memory	1000

💡 At step 4, request 1100 is greater than available memory 1000, so allocation fails.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4
memoryPool	1000	700	700	1000	1000
request	300	300	300	300	1100

Key Moments - 3 Insights

Why does memoryPool decrease at step 1?

Because the requested memory (300) is allocated, so memoryPool reduces from 1000 to 700 as shown in execution_table row 1.

Why does memoryPool return to 1000 at step 3?

At step 3, the allocated memory is freed, adding back 300 to memoryPool, restoring it to 1000 as in execution_table row 3.

What happens if requested memory is more than available?

At step 4, request 1100 is greater than memoryPool 1000, so allocation fails and memoryPool stays unchanged, as shown in execution_table row 4.

Visual Quiz - 3 Questions

Look at the execution table, what is memoryPool after step 1?

A 300

B 700

C 1000

D 0

💡 Hint

Check the 'memoryPool After' column in row for step 1.

At which step does the memory get freed back to the pool?

A Step 3

B Step 1

C Step 2

D Step 4

💡 Hint

Look for the action 'Free 300 memory' in the execution table.

If request was 1200 instead of 1100 at step 4, what would happen?

A MemoryPool becomes negative

B Memory allocated successfully

C Error: Out of Memory

D MemoryPool increases

💡 Hint

Refer to the condition check and action at step 4 in the execution table.

Concept Snapshot

Memory allocation in blockchain:
- Request memory from pool
- Check if enough memory is available
- Allocate memory (reduce pool)
- Use memory
- Free memory (restore pool)
- If request > available, throw error

Full Transcript

This visual execution shows how memory allocation works in blockchain programming. We start with a memory pool of 1000 units. When a request for 300 units comes, we check if the pool has enough memory. Since 300 is less than 1000, we allocate it, reducing the pool to 700. Then we use the memory (no change in pool). After usage, we free the memory, adding 300 back to the pool, restoring it to 1000. If a request exceeds available memory, like 1100, allocation fails and the pool stays the same. This process ensures safe memory management during blockchain transactions.