tep_free_plugin_paths() function in libtraceevent

tep_free_plugin_paths() function in libtraceevent

[Ben Hutchings]

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I noticed that the new function tep_free_plugin_paths() is exported
from libtraceevent, but is only declared in a private header file.

If it's meant to be part of the API, it should be declared in a public
header file.  If not, I think it should be hidden from library users.

(I think there are other only functions with this issue; this just came
to my attention because the Debian packaging tools prompted me to
update the symbol-to-minimum-version mapping.)

Ben.

-- 
Ben Hutchings
Never put off till tomorrow what you can avoid all together.


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Re: tep_free_plugin_paths() function in libtraceevent

[Arnaldo Carvalho de Melo]

Em Fri, Sep 11, 2020 at 03:08:16AM +0100, Ben Hutchings escreveu:
> I noticed that the new function tep_free_plugin_paths() is exported
> from libtraceevent, but is only declared in a private header file.
> 
> If it's meant to be part of the API, it should be declared in a public
> header file.  If not, I think it should be hidden from library users.
> 
> (I think there are other only functions with this issue; this just came
> to my attention because the Debian packaging tools prompted me to
> update the symbol-to-minimum-version mapping.)

Tzvetomir, can you please take a look?

- Arnaldo

Re: tep_free_plugin_paths() function in libtraceevent

[Tzvetomir Stoyanov]

On Tue, Sep 15, 2020 at 12:29 AM Arnaldo Carvalho de Melo
<arnaldo.melo@gmail.com> wrote:
>
> Em Fri, Sep 11, 2020 at 03:08:16AM +0100, Ben Hutchings escreveu:
> > I noticed that the new function tep_free_plugin_paths() is exported
> > from libtraceevent, but is only declared in a private header file.

Hi Ben,
The tep_free_plugin_paths() function is supposed to be an internal
function, not an API - that's why it is in a private header. What do you
mean by "exported": the "tep_" prefix, or the fact that it is not static?
I can remove the prefix, if that is what bothers you. The function is
defined in event-plugin.c and is used in event-parse.c, that's why it
cannot be made static without a library redesign.

> >
> > If it's meant to be part of the API, it should be declared in a public
> > header file.  If not, I think it should be hidden from library users.
> >
> > (I think there are other only functions with this issue; this just came
> > to my attention because the Debian packaging tools prompted me to
> > update the symbol-to-minimum-version mapping.)
>
> Tzvetomir, can you please take a look?
>
> - Arnaldo



-- 
Tzvetomir (Ceco) Stoyanov
VMware Open Source Technology Center

Re: tep_free_plugin_paths() function in libtraceevent

[Ben Hutchings]

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On Tue, 2020-09-15 at 16:12 +0300, Tzvetomir Stoyanov wrote:
> On Tue, Sep 15, 2020 at 12:29 AM Arnaldo Carvalho de Melo
> <arnaldo.melo@gmail.com> wrote:
> > Em Fri, Sep 11, 2020 at 03:08:16AM +0100, Ben Hutchings escreveu:
> > > I noticed that the new function tep_free_plugin_paths() is exported
> > > from libtraceevent, but is only declared in a private header file.
> 
> Hi Ben,
> The tep_free_plugin_paths() function is supposed to be an internal
> function, not an API - that's why it is in a private header. What do you
> mean by "exported": the "tep_" prefix, or the fact that it is not static?

It is exported from the shared library, i.e. it's included in the
library's dynamic symbols.  That means that it could be called by a
program using the library, and would conflict with a function defined
by the program.

> I can remove the prefix, if that is what bothers you.

No, exporting symbols without that prefix would make conflicts more
likely.

> The function is
> defined in event-plugin.c and is used in event-parse.c, that's why it
> cannot be made static without a library redesign.

Yes, I realise that.  However you can define it as "hidden":
<https://gcc.gnu.org/onlinedocs/gcc-10.2.0/gcc/Common-Function-Attributes.html#index-visibility-function-attribute>.

Ben.

> > > If it's meant to be part of the API, it should be declared in a public
> > > header file.  If not, I think it should be hidden from library users.
> > > 
> > > (I think there are other only functions with this issue; this just came
> > > to my attention because the Debian packaging tools prompted me to
> > > update the symbol-to-minimum-version mapping.)
> > 
> > Tzvetomir, can you please take a look?
> > 
> > - Arnaldo
> 
> 
-- 
Ben Hutchings
I'm not a reverse psychological virus.
Please don't copy me into your signature.


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Re: tep_free_plugin_paths() function in libtraceevent

[Steven Rostedt]

On Tue, 15 Sep 2020 14:26:48 +0100
Ben Hutchings <ben@decadent.org.uk> wrote:

> On Tue, 2020-09-15 at 16:12 +0300, Tzvetomir Stoyanov wrote:
> > On Tue, Sep 15, 2020 at 12:29 AM Arnaldo Carvalho de Melo
> > <arnaldo.melo@gmail.com> wrote:  
> > > Em Fri, Sep 11, 2020 at 03:08:16AM +0100, Ben Hutchings escreveu:  
> > > > I noticed that the new function tep_free_plugin_paths() is exported
> > > > from libtraceevent, but is only declared in a private header file.  
> > 
> > Hi Ben,
> > The tep_free_plugin_paths() function is supposed to be an internal
> > function, not an API - that's why it is in a private header. What do you
> > mean by "exported": the "tep_" prefix, or the fact that it is not static?  
> 
> It is exported from the shared library, i.e. it's included in the
> library's dynamic symbols.  That means that it could be called by a
> program using the library, and would conflict with a function defined
> by the program.

Of course a program that uses this shouldn't have any tep_ prefix
functions ;-)

> 
> > I can remove the prefix, if that is what bothers you.  
> 
> No, exporting symbols without that prefix would make conflicts more
> likely.

Right!

> 
> > The function is
> > defined in event-plugin.c and is used in event-parse.c, that's why it
> > cannot be made static without a library redesign.  
> 
> Yes, I realise that.  However you can define it as "hidden":
> <https://gcc.gnu.org/onlinedocs/gcc-10.2.0/gcc/Common-Function-Attributes.html#index-visibility-function-attribute>.

Ah, that's how libraries can hide non static functions. I learned something
new today!

Tzvetomir,


Let's only have functions that are part of the library's API start with
"tep_", and all other functions not have "tep_" in the name (so we know
which ones are exported and which ones are not).

Then any function that doesn't start with "tep_" should either be static,
or hidden.

#define __hidden __attribute__((visibility ("hidden")))

static void foo ()
{
}

void __hidden bar ()
{
}


-- Steve