[OpenJDK 2D-Dev] <AWT Dev> RFR: Allow using the system libjpeg

[Omair Majid]

* Andrew Hughes <gnu.andrew at redhat.com> [2014-05-21 20:23]:
> ----- Original Message -----
> > * Andrew Hughes <gnu.andrew at redhat.com> [2014-05-21 12:22]:
> > > I'm not keen on the hardcoding of '-ljpeg'
> > > 
> > > +  LIBJPEG_LIBS := -ljpeg
> > 
> > There's no pkg-config files for it. Any suggestions on how to get
> > something generic?
> > 
> 
> I know there isn't at present. I still think it's better to be consistent
> and set the values in configure, even if at present they have to be hardcoded
> defaults.

Would you mind if I did this as a separate patch? I will need to fix
other libraries too (libzip, and libgif).

> The make documentation is a little unclear here, and makes it sound like it
> will always be set if := or = is used.

Indeed, it is unclear. But I discovered through trial and error that
given a Makefile like:

FOO=-v
all:
	gcc ${FOO}

these two forms are different:

$ FOO=bar make

$ make FOO=bar

The first one sets the environment variable FOO, and the Makefile
overrides it (it runs `gcc -v`). The second passes a command line
argument that overrides the value in the Makefile (it runs `gcc foo`).

Thanks,
Omair

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