1248534 - Remove unused XPT features

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[Nicholas Nethercote [inactive]]

We can remove some XPT code.

Comment 1

[Nicholas Nethercote [inactive]]

Attachment: (part 1) - Remove XPT encoding support

Currently XPT can both encode and decode, but encoding has been handled by
Python code since bug 643817, so the encoding support can be removed. This
results in many simplifications. Some notable changes:

- All the XPTHashTable code (including XPTDatapool::offset_map) is no longer
  necessary.

- PrimitiveTest.cpp and SimpleTypeLib.cpp both don't make much sense without
  encoding support, so I removed them.

- A lot of the version code was already unused, e.g. XPT_VERSION_*,
  XPT_TYPELIB_VERSIONS_STRUCT, XPT_TYPELIB_VERSIONS.
  XPT_MAJOR_INCOMPATIBLE_VERSION is the only thing actually used in version
  checks.

- The patch also removes some code that was dead even before encoding removal,
  such as XPT_ParseVersionString().

Comment 2

[Nicholas Nethercote [inactive]]

For part 1 we have:

 9 files changed, 107 insertions(+), 1423 deletions(-)

Comment 3

[Nicholas Nethercote [inactive]]

Attachment: (part 2) - Remove unused XPT flags

Comment 4

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

FWIW, while I will do these reviews, they are quite low priority to me.

Comment 5

[Nicholas Nethercote [inactive]]

The XPT_ENCODE removal was inspired by part 1 of bug 1249174 -- removing the argnum2 field is easier when we don't have to worry about encoding.

Comment 6

[Nicholas Nethercote [inactive]]

Attachment: (part 3) - Remove almost all support for XPT annotations

PT supports annotations but xpt.py doesn't generate them except for a single
empty annotation (to indicate there are no real annotations). So we can remove
almost all support for them. This also allows XPTString to be removed.

Comment 7

[Nicholas Nethercote [inactive]]

Attachment: (part 4) - Remove unused fields from XPTConstValue

Comment 8

[Nicholas Nethercote [inactive]]

Attachment: (part 5) - Remove XPTDatapool

It can just be inlined into XPTState, which simplifies things.

Comment 9

[Nicholas Nethercote [inactive]]

Attachment: (part 6) - Stack-allocate XPTState

RegisterBuffer() is the only place that creates an XPTState, and it also
destroys it. So the XPTState can be allocated on the stack, which voids the
need for the creation of an XPTArena.

Comment 10

[Nicholas Nethercote [inactive]]

Attachment: (part 7) - Only define XPTArena::name if XPT_ARENA_LOGGING is defined

Comment 11

[Nicholas Nethercote [inactive]]

Attachment: (part 8) - Remove useless XPT freeing code

PT has some functions and macros for freeing memory. However, they (a) are
only used on error paths, and (b) don't actually free memory -- they just
optionally log the "freeing" -- because piecewise freeing doesn't make sense
with arena allocation.

This patch removes all that unnecessary machinery.

Comment 12

[Nicholas Nethercote [inactive]]

Attachment: (part 9) - Remove XPT arena logging code

I bet nobody has used this code in a decade. I haven't, even though I've been
working on reducing XPT memory usage. Well-targeted diagnostic printfs are much
more useful than these kind of overview stats, in my experience.

Comment 13

[Nicholas Nethercote [inactive]]

These 9 patches reduce the number of lines of code in xpcom/typelib/xpt/*.{h,cpp} from 2680 to 1316, and the diffstat overall is as follows:

 13 files changed, 142 insertions(+), 1805 deletions(-)

Comment 14

[Nicholas Nethercote [inactive]]

Attachment: (part 4) - Remove unused fields from XPTConstValue

(I tweaked a comment.)

Comment 15

[Nicholas Nethercote [inactive]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/56f75a8f44915a4468fbedaf3beb9767b73eb343
Bug 1248534 (part 1) - Remove XPT encoding support. r=khuey.

https://hg.mozilla.org/integration/mozilla-inbound/rev/475874efad984c2141afd6818007f48846999d46
Bug 1248534 (part 2) - Remove unused XPT flags. r=khuey.

https://hg.mozilla.org/integration/mozilla-inbound/rev/14ba54064f33d9dc0dbcdca7ebd2dff582973fcf
Bug 1248534 (part 3) - Remove almost all support for XPT annotations. r=khuey.

https://hg.mozilla.org/integration/mozilla-inbound/rev/a0ce7857613ec423ec143fb3c22c3eee8646fd4e
Bug 1248534 (part 4) - Remove unused fields from XPTConstValue. r=khuey.

https://hg.mozilla.org/integration/mozilla-inbound/rev/25c818450f3229d4b3904f5eb8a27c4a4d6fb27c
Bug 1248534 (part 5) - Remove XPTDatapool. r=khuey.

https://hg.mozilla.org/integration/mozilla-inbound/rev/76740f3273fb519efe26f1dd345be20f5c9668d0
Bug 1248534 (part 6) - Stack-allocate XPTState. r=khuey.

https://hg.mozilla.org/integration/mozilla-inbound/rev/d380cae049a102d96f94523fab6af90ae324a35a
Bug 1248534 (part 8) - Remove useless XPT freeing code. r=khuey.

https://hg.mozilla.org/integration/mozilla-inbound/rev/d429066578eb056ca2b9cd110cca8b63490c4d9b
Bug 1248534 (part 9) - Remove XPT arena logging code. r=khuey.

Comment 16

[Nicholas Nethercote [inactive]]

Whoops, part 7 didn't get mentioned in comment 15 because I mistakenly put bug 1249174 in the commit message. No matter. See also bug 1249174 comment 15.

Comment 17

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/56f75a8f4491
https://hg.mozilla.org/mozilla-central/rev/475874efad98
https://hg.mozilla.org/mozilla-central/rev/14ba54064f33
https://hg.mozilla.org/mozilla-central/rev/a0ce7857613e
https://hg.mozilla.org/mozilla-central/rev/25c818450f32
https://hg.mozilla.org/mozilla-central/rev/76740f3273fb
https://hg.mozilla.org/mozilla-central/rev/d380cae049a1
https://hg.mozilla.org/mozilla-central/rev/d429066578eb