Bug 25996 – [Qt] Dead-code stripping for unix

• Component: WebKit Qt
• Status: RESOLVED FIXED

[Laszlo Gombos]

Turn on dead-code stripping for the Qt port - Unix (no Mac) and GCC only.

In default configuration, this change reduced the binary size by ~6% (with 1.23 Mb); removed ~3900 dead symbols (statistics based on r44115)

[Laszlo Gombos]

Created attachment 30633 [details]
Turn on GCC dead-code stripping flags for Unix

[Laszlo Gombos]

(In reply to comment #0)
> Turn on dead-code stripping for the Qt port - Unix (no Mac) and GCC only.
> In default configuration, this change reduced the binary size by ~6% (with 1.23
> Mb); removed ~3900 dead symbols (statistics based on r44115)

Cross the dead symbol statistics, it should be less than the number I gave..

[Holger Freyther]

Do you have a list of dead symbols?

[Laszlo Gombos]

Created attachment 30654 [details]
List of dead symbols - Qt port on Linux

~ 3400 dead symbols; my initial numbers were not far off; Interesting list to scan trough.

[Holger Freyther]

Comment on attachment 30633 [details]
Turn on GCC dead-code stripping flags for Unix

I'm a bit sad. I had the hope that the linker would remove these symbols... the other sad part is linking time will be slighly increased now?

[Holger Freyther]

Landed in r44179. Thanks.

[Simon Hausmann]

On the top of the list of the dead symbols is _NPN_IntFromIdentifier, which is used right in PluginPackage.cpp (the address of the symbol is taken, so it can't be inlined). How did you generate the list? Was it generated on a build without netscape plugin support?

[Laszlo Gombos]

Created attachment 31411 [details]
Regenerated dead symbol list for r44682

[Laszlo Gombos]

(In reply to comment #7)
> On the top of the list of the dead symbols is _NPN_IntFromIdentifier, which is
> used right in PluginPackage.cpp (the address of the symbol is taken, so it
> can't be inlined). How did you generate the list? Was it generated on a build
> without netscape plugin support?

I regenerated the dead symbol list (QtWebKit release build on Linux) and _NPN_IntFromIdentifier no longer shows up as dead symbol (I do not have an explanation how the _NPN_IntFromIdentifier symbol ended up in the previous list). 

Here is a brief explanation on how I generated the list:
 - Make two builds; one with dead symbol stripping, one without it
 - Get all the defined symbols in each .so by running nm --defined-only
 - Get the delta of from the two symbol list and demangle the symbols with c++filt