[poppler] Why does Gfx::opTab need to be built at runtime?

[Jeff Muizelaar]

On Wed, Sep 26, 2007 at 11:43:35AM -0700, Krzysztof Kowalczyk wrote:
> On 9/26/07, Albert Astals Cid <aacid at kde.org> wrote:
> > A Dimarts 25 Setembre 2007, Krzysztof Kowalczyk va escriure:
> > > I'm looking at optimizing poppler in  various ways and just noticed
> > > something I don't understand. I hope someone will be able to enlighten
> > > me.
> > >
> > > In Gfx.h there is:
> > >
> > > struct Operator {
> > >   char name[4];
> > >   int numArgs;
> > >   TchkType tchk[maxArgs];
> > >   void (Gfx::*func)(Object args[], int numArgs);
> > > };
> > >
> > > and in Gfx.cc a table is filled out like this:
> > >
> > > Operator Gfx::opTab[] = {
> > >   {"\"",  3, {tchkNum,    tchkNum,    tchkString},
> > >           &Gfx::opMoveSetShowText},
> > >
> > > According to a profiler, at least on Windows, the single biggest
> > > function in poppler (~9k) is anonymous function constructed by the
> > > compiler to fill out Gfx::opTab.
> >
> > What do you exactly mean with ~9k ?
> 
> It means that behind the scenes a compiler generates a function that
> is 9k of assembly code (that is in optimized msvc build) and all it
> does is constructing this table at runtime, even though I would hope
> all this data is known statically and could be simply stored in data
> section.
> 
> Changing char name[4] to char* name saves 1k of code.
> 
> Adding const doesn't change anything.
> 
> Ultimately I would like to find a way to force compiler to fully build
> it at compile time.
> 
> I haven't looked at what gcc produces but it should be apparent after
> looking at map file of inspecting symbol table.

gcc does not produce any code for this afaict. I can't understand why
visualc would be, unless you are just disassembling the .data section.

-Jeff