CODEWITHSUNDEEP
gdb
Matthew Hoggan
Matthew Hoggan

Reputation: 7594

gdb: how to view all memory associated with struct in hex

I have a pointer to a struct and I can print it in gdb using print /x (*s).

However this gives me:

..., intensity = 2 '\002'}, {distance_2cm = 3045, intensity = 3 '\003'}, {distance_2cm = 14735, intensity = 7 '\a'}, {dis tance_2cm = 3345, intensity = 3 '\003'}, {distance_2cm = 14272, intensity = 7 '\a'}, {distance_2cm = 3735, intensity = 2 '\002'}, {distance_2cm = 14617, intensity = 6 '\006'}, {distance_2cm = 4239, intensity = 2 '\002'}, {distance_2cm = 9741, intensity = 5 '\005'}, {distance_2cm = 4892, intensity = 2 '\002'}, {distance_2cm = 10686, intensity = 4 '\004' }, {distance_2cm = 6012, intensity = 3 '\003'}, {distance_2cm = 9906, intensity = 3 '\003'}}}, {head = {laser_block_id = 61183, rotational_theta = 21191}, lasers_arary = {{distance_2cm = 0, intensity = 2 '\002'}, {distance_2cm = 0, inte nsity = 1 '\001'}, {distance_2cm = 0, intensity = 3 '\003'}, {distance_2cm = 0, intensity = 1 '\001'}, {distance_2cm = 0, intensity = 2 '\002'}, {distance_2cm = 0, intensity = 2 '\002'}, {distance_2cm = 0, intensity = 1 '\001'}, {distan ce_2cm = 6426, intensity = 1 '\001'}, {distance_2cm = 2040, intensity = 3 '\003'}, {distance_2cm = 6584, intensity = 2 '\002'}, {distance_2cm = 2154, intensity = 3 '\003'}, {distance_2cm = 0, intensity = 1 '\001'}, {distance_2cm = 2282, intensity = 3 '\003'}, {distance_2cm = 0, intensity = 1 '\001'}, {distance_2cm = 2428, intensity = 2 '\002'}, {distan ce_2cm = 26580, intensity = 33 '!'}, {distance_2cm = 2592, intensity = 5 '\005'}, {distance_2cm = 27180, intensity = 2 7 '\033'}, {distance_2cm = 2795, intensity = 3 '\003'}, {distance_2cm = 0, intensity = 2 '\002'}, {distance_2cm = 3045 , intensity = 3 '\003'}, {distance_2cm = 14712, intensity = 22 '\026'}, {distance_2cm = 3342, intensity = 3 '\003'}, { distance_2cm = 14181, intensity = 7 '\a'}, {distance_2cm = 3729, intensity = 2 '\002'}, {distance_2cm = 14474, intensi ty = 6 '\006'}, {distance_2cm = 4228, intensity = 2 '\002'}, {distance_2cm = 9744, intensity = 1 '\001'}, {distance_2c m = 4887, intensity = 2 '\002'}, {distance_2cm = 13075, intensity = 7 '\a'}, {distance_2cm = 5994, intensity = 3 '\003 '}, {distance_2cm = 9947, intensity = 4 '\004'}}}, {head = {laser_block_id = 61183, rotational_theta = 21207}, lasers_ arary = {{distance_2cm = 0, intensity = 2 '\002'}, {distance_2cm = 0, intensity = 1 '\001'}, {distance_2cm = 0, intens ity = 3 '\003'}, {distance_2cm = 0, intensity = 1 '\001'}, {distance_2cm = 0, intensity = 2 '\002'}, {distance_2cm = 0 , intensity = 2 '\002'}, {distance_2cm = 0, intensity = 1 '\001'}, {distance_2cm = 0, intensity = 1 '\001'}, {distance _2cm = 2038, intensity = 6 '\006'}, {distance_2cm = 6548, intensity = 1 '\001'}, {distance_2cm = 2146, intensity = 3 ' \003'}, {distance_2cm = 0, intensity = 1 '\001'}, {distance_2cm = 2285, intensity = 3 '\003'}, {distance_2cm = 0, inte nsity = 1 '\001'}, {distance_2cm = 2428, intensity = 2 '\002'}, {distance_2cm = 26498, intensity = 33 '!'}, {distance_ 2cm = 2590, intensity = 5 '\005'}, {distance_2cm = 26177, intensity = 29 '\035'}, {distance_2cm = 2792, intensity = 3 '\003'}, {distance_2cm = 0, intensity = 2 '\002'}, {distance_2cm = 3044, intensity = 3 '\003'}, {distance_2cm = 14743, intensity = 7 '\a'}, {distance_2cm = 3344, intensity = 3 '\003'}, {distance_2cm = 14147, intensity = 7 '\a'}, {distan ce_2cm = 3728, intensity = 2 '\002'}, {distance_2cm = 14520, intensity = 13 '\r'}, {distance_2cm = 4222, intensity = 2 '\002'}, {distance_2cm = 14567, intensity = 5 '\005'}, {distance_2cm = 4885, intensity = 3 '\003'}, {distance_2cm = 1 0842, intensity = 6 '\006'}, {distance_2cm = 5978, intensity = 3 '\003'}, {distance_2cm = 9964, intensity = 6 '\006'}} }}}, sd = {gps_time_stamp = 59467414, status_type = 55 '7', status_value = 33 '!'}}

I want to view it in hex, something like the hypothetical output below:

00000000: 2369 6e63 6c75 6465 203c 6368 6563 6b2e
00000010: 683e 0a0a 2369 6e63 6c75 6465 2022 635f
00000020: 7665 6c6f 6479 6e65 2f61 7267 7061 7273
00000030: 652e 6822 0a23 696e 636c 7564 6520 2263

Is there a way to do this with gdb?

Upvotes: 1

Views: 4269

Answers (1)

Tom Tromey
Tom Tromey

Reputation: 22549

This can be done with the x command. The simplest way is to first find the size of your structure, and then pass this as an argument to x. Something like:

(gdb) print sizeof(whatever)
$1 = 1024
(gdb) x/512xh &whatever

Decoding x/512xh:

  • 512 is the repeat count, here half the size of the structure, because your example showed 2 bytes per word;
  • x means print in hex;
  • h means "halfword", aka 2 bytes.

The gdb manual explains all the flags that can be used here.

You can do this in a fancier way using eval to compute the length for you. If you're doing this a lot I would suggest perhaps writing a new command in Python that does a bit of processing and then invokes x.

Upvotes: 7

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