Is it possible to enable data sections and function sections without explicitly giving flags "-fdata-sections" and "-ffunction-sections"?

Is it possible to enable data sections and function sections without explicitly giving flags "-fdata-sections" and "-ffunction-sections"?

[3119369616.qq]

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To divide functions into sections and then remove unused sections, I must provide flags "-fdata-sections" and "-ffunction-sections" in GCC and a flag "--gc-sections" in LD. Most of the build systems don't support these flags so GCC will generate bigger binaries.
Is it possible to enable this feature without  giving any command line flags manually?

Re: Is it possible to enable data sections and function sections without explicitly giving flags "-fdata-sections" and "-ffunction-sections"?

[Arsen Arsenović]

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"3119369616.qq via Gcc" <gcc@gcc.gnu.org> writes:

> To divide functions into sections and then remove unused sections, I must
> provide flags "-fdata-sections" and "-ffunction-sections" in GCC and a flag
> "--gc-sections" in LD. Most of the build systems don't support these flags so
> GCC will generate bigger binaries.
> Is it possible to enable this feature without&nbsp; giving any command line flags manually?

All (at least decent) build systems support passing extra flags to the
compiler and linker (e.g. CXXFLAGS="-ffunction-sections"), or passing a
custom compiler and linker (which can set those flags, something like
CC="gcc -ffunction-sections").  This is how you should be setting such
flags.

If you're interested in DCE and other size-reducing optimizations, you
might also be interested in LTO and -Os.
-- 
Arsen Arsenović

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Re: Is it possible to enable data sections and function sections without explicitly giving flags "-fdata-sections" and "-ffunction-sections"?

[David Brown]

On 19/03/2023 13:38, 3119369616.qq via Gcc wrote:
> To divide functions into sections and then remove unused sections, I
> must provide flags "-fdata-sections" and "-ffunction-sections" in GCC
> and a flag "--gc-sections" in LD. Most of the build systems don't
> support these flags so GCC will generate bigger binaries. Is it
> possible to enable this feature without  giving any command line
> flags manually?

Just to be clear here - removing unused sections is only beneficial if 
you have a significant amount of unused code and data compiled in the 
build.  That can sometimes be the case, if you are making re-usable 
library code.  But for other types of code, it is better to be clear in 
the source code about what is and is not part of the program - i.e., if 
the function is not used by the program, it should not be in the source 
code.  I don't know what kind of code you are working on, but it's worth 
considering.