[jamming] Jam2.5 and precompiled headers

Elliot Murphy elliot.murphy at veritas.com
Sat Feb 1 09:37:39 PST 2003


Without knowing exactly what error you're getting from visual c++,
we had trouble on parallel builds with vc++ until we added the /Fd
switch, which allows you to specify which name should be used
for the pdb file. (I haven't done this with jam yet or I would post
more details).
-elliot

|-----Original Message-----
|From: Matt Armstrong [mailto:matt at lickey.com] 
|Sent: Saturday, February 01, 2003 11:56 AM
|To: Chris Antos
|Cc: Jacob Gorm Hansen; jam mailling list
|Subject: Re: [jamming] Jam2.5 and precompiled headers
|
|
|"Chris Antos" <chrisant at windows.microsoft.com> writes:
|
|> I said you get maximum win from batch compilation WHEN YOU USE
|> PRECOMPILED HEADERS.  :-)  (caps to add visibility to key point)
|
|Interestingly, I see performance gains of 70-80% when a whole library
|is turned into a single .c file (e.g. add one .c file that #includes
|all the others and compile that).
|
|Unfortunately this doesn't always work, given the semantics of a C
|compilation unit.
|
|
|> Between batch compilation and precompiled headers, the latter gives
|> a bigger win.  Combining the two gains some additional improvements
|
|I've also looked into trying to get visual c++ to support parallel
|builds (-j 2).  Unfortunately, the compiler barfs because it wants to
|build a .pdb file.  :-(
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