Since commit v3.4.0-rc1~321^2~2 (Genex: Store a backtrace, not a pointer
to one, 2015-07-08) we treat cmListFileBacktrace instances as
lightweight values. This was true at the time only because the
backtrace information was kept in the cmState snapshot hierarchy.
However, that forced us to accumulate a lot of otherwise short-lived
snapshots just to have the backtrace fields available for reference by
cmListFileBacktrace instances. Recent refactoring made backtrace
instances independent of the snapshot hierarchy to avoid accumulating
short-lived snapshots. This came at the cost of making backtrace values
heavy again, leading to lots of string coying and slower execution.
Fix this by refactoring cmListFileBacktrace to provide value semantics
with efficient shared storage underneath. Teach cmMakefile to maintain
its call stack using an instance of cmListFileBacktrace. This approach
allows the current backtrace to be efficiently saved whenever it is
needed.
Also teach cmListFileBacktrace the notion of a file-level scope. This
is useful for messages about the whole file (e.g. during parsing) that
are not specific to any line within it. Push the CMakeLists.txt scope
for each directory and never pop it. This ensures that we always have
some context information and simplifies cmMakefile::IssueMessage.
Push/pop a file-level scope as each included file is processed. This
supersedes cmParseFileScope and improves diagnostic message context
information in a few places. Fix the corresponding test cases to expect
the improved output.
Changes during post-3.3/pre-3.4 development refactored storage of most
configure-time information, including variable bindings and function
scopes. All scopes (even short-lived) were kept persistently for
possible future debugging features, causing huge accumulated memory
usage. This was mostly addressed by commit v3.4.1~4^2 (cmState: Avoid
accumulating snapshot storage for short-lived scopes, 2015-11-24).
Since then we still keep short-lived scopes when they are needed for a
backtrace. This is because since commit v3.4.0-rc1~378^2
(cmListFileBacktrace: Implement in terms of cmState::Snapshot,
2015-05-29) backtraces have been lightweight objects that simply point
into the snapshot tree. While the intention of this approach was to
avoid duplicating the call stack file path strings, the cost turned out
to be holding on to the entire call stack worth of scope snapshots,
which is much worse.
Furthermore, since commit v3.4.0-rc2~1^2 (cmIfCommand: Issue CMP0054
warning with appropriate context, 2015-10-20) all conditions used in
`if()` commands hold a backtrace for use in diagnostic messages. Even
though the backtrace is short-lived it still causes the scope snapshot
to be kept. This means that code like
function(foo)
if(0)
endif()
endfunction()
foreach(i RANGE 1000000)
foo()
endforeach()
accumulates storage for the function call scope snapshots.
Fix this by partially reverting commit v3.4.0-rc1~378^2 and saving the
entire call stack during cmListFileBacktrace construction. This way
we can avoid keeping short-lived scope snapshot storage in all cases.
Add new API for the subdirs command to cmState.
This fixes a regression introduced in commit f716460e (cmMakefile: Move
invokation to initialize snapshot., 2015-10-06).
637c56b4 cmGlobalGenerator: Implement FillProjectMap in terms of cmState.
b3f2299e cmState: Move ProjectName from cmMakefile.
6ce940ac cmMakefile: Use std::string in ProjectName API.
e8c0341d cmMakefile: Out-of-line GetProjectName.
867b5be8 cmLocalGenerator: Remove unused Children member.
6c832219 cmLocalGenerator: Implement child traversal in terms of cmState.
3fcf3837 Makefiles: Remove valueless cast.
223f4a66 cmLocalGenerator: Simplify condition.
ae026f54 cmState: Store Children states in parent state.
59e21ffa Port static calls from cmLocalGenerator to cmOutputConverter.
242dcc2c cmListFileBacktrace: Replace local generator with cmState::Snapshot.
1cff330b cmTarget: Port to cmOutputConverter.
2f1bd62b cmCustomCommandGenerator: Port to cmOutputConverter.
0f2a1324 cmCommandArgumentParserHelper: Port to cmOutputConverter.
4d8b79ad cmComputeLinkInformation: Port to cmOutputConverter.
8680520f cmMakefile: Make the cmState::Snapshot accessible.
6d7abb63 cmOutputConverter: Extract from cmLocalGenerator.
a8244157 cmState::Snapshot: Provide accessor for the cmState.
1f4ef396 cmLocalGenerator: Remove some commented lines of code.
This will be used to contain most of the content of the cmState
in several different trees. Refer to the BuildsystemDirectory
state from the SnapshotData state. Currently these trees have
the same structure, but that will change when we have more snapshot
types.
Brad King
Stephen Kelly