What is -fdata-sections in gcc?

RE: What is -fdata-sections in gcc?

_maibi — Thu, 13 Jun 2019 10:37:17 GMT

This is what happens when I try to access the wrong handler address.

my actual handler address is 0x200010 (example).

and compare value of variable containing handler address in another module.

it is contaminated partially.

(gdb) print actual_handler

0x200010

(gdb) print m_evt_handler ( in another module)

0x2000ff

so I try to debugging upper m_evt_handler address.

(gdb) x/256b (m_evt_handler address-0x80)

0x20004a58 <m_read_buf>: 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff

....

0x20004aXX <m_read_buf>: 0xff 0xff 0xff 0xff 0xff 0xff 0xff 0xff

0x20004aXX <m_evt_handler>: 0xff 0x00 0x20 ....

and I check the usage of m_read_buf in my code. and I found overrun bug.

RE: What is -fdata-sections in gcc?

awneil — Thu, 13 Jun 2019 10:13:32 GMT

[quote userid="72896" url="~/f/nordic-q-a/48438/what-is--fdata-sections-in-gcc/192624"]finally I found the bug![/quote]

For the benefit of other readers who may come along with similar problems, please describe what was the bug.

And how did you find it?

RE: What is -fdata-sections in gcc?

_maibi — Thu, 13 Jun 2019 10:11:30 GMT

as your mention, I concentrate debugging overriding memory, finally I found the bug!! thank your advice!

RE: What is -fdata-sections in gcc?

Vidar Berg — Wed, 12 Jun 2019 11:58:37 GMT

Yes, verify that the function pointer stays the same by using the if check you had earlier (m_conn_params_config.evt_handler). The event number is invalid which may be a sign of a buffer overrun.

RE: What is -fdata-sections in gcc?

_maibi — Wed, 12 Jun 2019 09:47:30 GMT

hi! thanks for response, I checked that this was not a flag problem.

same stack trace occur... I just modified my code a little and compiled it.

what should I do next step for debugging? It's really hard to me.

RE: What is -fdata-sections in gcc?

awneil — Wed, 12 Jun 2019 09:01:17 GMT

[quote userid="72896" url="~/f/nordic-q-a/48438/what-is--fdata-sections-in-gcc/192018"]Is this flag related on memory alignment[/quote][quote userid="4240" url="~/f/nordic-q-a/48438/what-is--fdata-sections-in-gcc/192275"]No, not directly at least[/quote]

Indeed.

I think it is possible to specify the alignment for a Section - but there's no inherent relation.

RE: What is -fdata-sections in gcc?

Vidar Berg — Wed, 12 Jun 2019 08:57:49 GMT

No, not directly at least. Do you still get the same stack trace that you posted in the other thread? It did not indicate an aligment issue.

RE: What is -fdata-sections in gcc?

_maibi — Tue, 11 Jun 2019 11:06:38 GMT

Is this flag related on memory alignment?

if so, Is it possible that Hardfault I suffered is related on m0 memory unalignment?

if it make sense, how I can debug where this error occur?

RE: What is -fdata-sections in gcc?

awneil — Tue, 11 Jun 2019 10:04:09 GMT

It's just a way of collecting data together in memory

https://gcc.gnu.org/onlinedocs/gcc-6.1.0/gccint/Sections.html