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Memory Dump Commands

Describes how to use the m command to get a dump of memory.

This command has two formats:

m start end

m start+length

Using the first format you provide the start and end addresses that you want to inspect; for example:

m 81240000 8124003F

Using the second form you provide the start address and the number of bytes to dump (in hex); for example:

m 81240000 +40

Both of the above examples dump 64 bytes from address 0x81240000. The output is a standard hex-dump:

.m 81240000 +40
81240000: 00 00 FF EB 08 01 BF D7 00 04 7D B6 02 00 BF EF ..........}.....
81240010: 00 01 DF EE 0A 40 7F F7 00 80 BF FF 20 10 FF EA .....@...... ...
81240020: 00 82 FF 77 04 24 FD FF 40 01 FF 7F 00 01 FF FF ...w.$..@.......
81240030: 08 10 FF BF 08 00 BF DE 08 00 EF FB 00 00 FF DF ................

Dumping the contents of classes

You can use the m command to inspect the contents of structures and class instances, but you need to be aware of a few things about the memory layout:

Symbian platform is little-endian, which means that all values are stored so that the least significant bytes are stored at the lower addresses in memory (or “backwards” as commonly perceived).

For example, the value 0x1234ABCD would be shown in the memory dump as:
```
CD AB 34 12
```
The compiler may add padding between variables either to speed up access or to avoid alignment restrictions; for example, words cannot be on odd addresses.

As an example, the following struct:
```
struct SExample
    {
    TUint8    iByte;
    TInt    iInteger;
    };
```
would be laid out in memory as:
```
+0(1)    iByte
+1(3)    padding
+4(4)    iInteger
```
The padding and alignment is compiler-dependent. Generally, fields must be aligned on a boundary equal to their size; for example, a TUint32 is 4 bytes wide so it must lie on a 4-byte boundary, i.e. the least significant two bits of the address must be zero.

When using GCC, classes which derive from CBase will have a virtual table pointer as the first word in the class data and classes which derive from DBase will have a virtual table pointer as the second word in the class data.

When using an EABI-compliant compiler, the virtual table pointer is always the first word of the class.

Parent topic: Debug Monitor Tool