Odd behavior with symbol naming mismatch between x86 and bfin platforms using version scripts

Odd behavior with symbol naming mismatch between x86 and bfin platforms using version scripts

[Kevin P. Fleming]

One of our developers is running into an issue with version scripts not
seeing symbols with the same naming scheme when code is built using GCC
on an x86 platform vs. using the Blackfin tools (versions listed below).
The attached files demonstrate the problem; when run as:

$ CC=cc CFLAG="-fPIC" ./mk

everything works as expected.

when run as:

$ CC=bfin-linux-uclibc-gcc CFLAG="-mfdpic " ./mk

the test fails, because the 'testcallback' function appears in the
dynamic symbol table as '_testcallback', and this the version script
causes it to be filtered out.

For x86 builds, we are using:

> gcc (Ubuntu 4.4.1-4ubuntu9) 4.4.1
> GNU ld (GNU Binutils for Ubuntu) 2.20

For Blackfin builds:

> bfin-linux-uclibc-gcc (ADI/svn-3473) 4.3.3
> GNU ld version 2.17

Is this a compiler bug, or a linker bug, or expected behavior?

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber: kpfleming@digium.com
Check us out at www.digium.com & www.asterisk.org

Re: Odd behavior with symbol naming mismatch between x86 and bfin platforms using version scripts

[Ian Lance Taylor]

"Kevin P. Fleming" <kpfleming@digium.com> writes:

> One of our developers is running into an issue with version scripts not
> seeing symbols with the same naming scheme when code is built using GCC
> on an x86 platform vs. using the Blackfin tools (versions listed below).
> The attached files demonstrate the problem; when run as:
>
> $ CC=cc CFLAG="-fPIC" ./mk
>
> everything works as expected.
>
> when run as:
>
> $ CC=bfin-linux-uclibc-gcc CFLAG="-mfdpic " ./mk
>
> the test fails, because the 'testcallback' function appears in the
> dynamic symbol table as '_testcallback', and this the version script
> causes it to be filtered out.
>
> For x86 builds, we are using:
>
>> gcc (Ubuntu 4.4.1-4ubuntu9) 4.4.1
>> GNU ld (GNU Binutils for Ubuntu) 2.20
>
> For Blackfin builds:
>
>> bfin-linux-uclibc-gcc (ADI/svn-3473) 4.3.3
>> GNU ld version 2.17
>
> Is this a compiler bug, or a linker bug, or expected behavior?

I think this counts as painful but expected behaviour.

One could imagine adding extern "C" along the lines of extern "C++" to
remove the leading underscore on targets which use one.  Or one could
imagine doing that automatically, although that would not be a
backward compatible change.

Ian

Re: Odd behavior with symbol naming mismatch between x86 and bfin platforms using version scripts

[Mike Frysinger]

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On Monday 08 February 2010 12:00:58 Kevin P. Fleming wrote:
> One of our developers is running into an issue with version scripts not
> seeing symbols with the same naming scheme when code is built using GCC
> on an x86 platform vs. using the Blackfin tools (versions listed below).

i already explained to Doug that the current behavior is correct:
http://blackfin.uclinux.org/gf/forummessage/85711
-mike

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