From: Bart Veer <bartv@redhat.com>
To: colin.ford@pipinghotnetworks.com
Cc: ecos-discuss@sources.redhat.com
Subject: Re: [ECOS] waitpid and alarm?
Date: Tue, 16 Jan 2001 08:19:00 -0000 [thread overview]
Message-ID: <200101161619.f0GGJZq20234@sheesh.cambridge.redhat.com> (raw)
In-Reply-To: <200101161536.PAA08774@colinf.pipinghotnetworks.com>
>>>>> "Colin" == Colin Ford <colin.ford@pipinghotnetworks.com> writes:
Colin> Thanks for the info Bart. The only thing is that I was put off somewhat
Colin> by the gcc info on the two option -ffunction-sections and
Colin> -fdata-sections,
Colin> see the last paragraph below:
Colin> @item -ffunction-sections
Colin> @itemx -fdata-sections
Colin> Place each function or data item into its own section in
Colin> the output file if the target supports arbitrary sections.
Colin> The name of the function or the name of the data item
Colin> determines the section's name in the output file.
This paragraph is correct - bearing in mind that eCos depends on
toolchains which support arbitrary sections.
Colin> Use these options on systems where the linker can perform
Colin> optimizations to improve locality of reference in the
Colin> instruction space. HPPA processors running HP-UX and Sparc
Colin> processors running Solaris 2 have linkers with such
Colin> optimizations. Other systems using the ELF object format as
Colin> well as AIX may have these optimizations in the future.
Correct to some extent: -ffunction-sections does allow linkers to
group related functions together. However as far as we are concerned
the main use is with the linker's --gc-sections option. This paragraph
really refers to native development rather than embedded systems.
Colin> Only use these options when there are significant benefits
Colin> from doing so.
In the eCos context and when linking with --gc-sections, there are
significant benefits.
Colin> When you specify these options, the assembler and linker
Colin> will create larger object and executable files and will
Colin> also be slower.
Only if the linker does not support --gc-sections.
Colin> You will not be able to use @code{gprof} on all systems if
Colin> you specify this option
This may be true, but currently we have no profiling support in eCos
so the issue has not been addressed.
Colin> and you may have problems with debugging if you specify
Colin> both this option and @samp{-g}.
This is software. There will be bugs. There may be bugs in the
compiler, linker, or gdb which only show up when using
-ffunction-sections. If there are such bugs then you may have
problems. So strictly speaking the statement is correct, but you can
say the same thing about all software.
There may well be problems when using debuggers other than gdb, for
example those debuggers might get confused by the large number of
sections. eCos users should not be affected.
Bart
prev parent reply other threads:[~2001-01-16 8:19 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-01-16 5:51 Colin Ford
2001-01-16 6:36 ` Bart Veer
2001-01-16 7:38 ` Colin Ford
2001-01-16 7:46 ` Gary Thomas
2001-01-16 9:52 ` Jonathan Larmour
2001-01-17 5:33 ` Colin Spier
2001-01-16 8:19 ` Bart Veer [this message]
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