Commit Graph

5749 Commits

Author SHA1 Message Date
Karasev Nikita 365c99fd7d Skip TemplateSpecializedType in modernize-pass-by-value.
Existing 'modernize-pass-by-value' check works only with non template values in
initializers. Fixes PR37210.
2020-02-28 09:17:16 -05:00
Nathan James 39c4246e1e [clang-tidy] Added virtual isLanguageVersionSupported to ClangTidyCheck
Summary:
Motivated by [[ https://bugs.llvm.org/show_bug.cgi?id=45045 | Tune inspections to a specific C++ standard. ]]
Moves the isLanguageVersionSupported virtual function from `MakeSmartPtrCheck` to the base `ClangTidyCheck` class.
This will disable registering matchers or pp callbacks on unsupported language versions for a check.
Having it as a standalone function is cleaner than manually disabling the check in the register function and should hopefully
encourage check developers to actually restrict the check based on language version.
As an added bonus this could enable automatic detection of what language version a check runs on for the purpose of documentation generation

Reviewers: aaron.ballman, gribozavr2, Eugene.Zelenko, JonasToth, alexfh, hokein

Reviewed By: gribozavr2

Subscribers: xazax.hun, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75289
2020-02-28 13:05:05 +00:00
Kadir Cetinkaya 48fad110e0
[clangd] Get rid of lexer usage in ObjCLocalizeStringLiteral tweak
Reviewers: hokein

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75230
2020-02-28 09:38:26 +01:00
Kadir Cetinkaya 98bb094c1e
[clangd] Use tokenize instead of raw lexer in SourceCode/lex
Reviewers: hokein, sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75249
2020-02-28 09:38:26 +01:00
Reid Kleckner 86565c1309 Avoid SourceManager.h include in RawCommentList.h, add missing incs
SourceManager.h includes FileManager.h, which is expensive due to
dependencies on LLVM FS headers.

Remove dead BeforeThanCompare specialization.

Sink ASTContext::addComment to cpp file.

This reduces the time to compile a file that does nothing but include
ASTContext.h from ~3.4s to ~2.8s for me.

Saves these includes:
    219 -    ../clang/include/clang/Basic/SourceManager.h
    204 -    ../clang/include/clang/Basic/FileSystemOptions.h
    204 -    ../clang/include/clang/Basic/FileManager.h
    165 -    ../llvm/include/llvm/Support/VirtualFileSystem.h
    164 -    ../llvm/include/llvm/Support/SourceMgr.h
    164 -    ../llvm/include/llvm/Support/SMLoc.h
    161 -    ../llvm/include/llvm/Support/Path.h
    141 -    ../llvm/include/llvm/ADT/BitVector.h
    128 -    ../llvm/include/llvm/Support/MemoryBuffer.h
    124 -    ../llvm/include/llvm/Support/FileSystem.h
    124 -    ../llvm/include/llvm/Support/Chrono.h
    124 -    .../MSVCSTL/include/stack
    122 -    ../llvm/include/llvm-c/Types.h
    122 -    ../llvm/include/llvm/Support/NativeFormatting.h
    122 -    ../llvm/include/llvm/Support/FormatProviders.h
    122 -    ../llvm/include/llvm/Support/CBindingWrapping.h
    122 -    .../MSVCSTL/include/xtimec.h
    122 -    .../MSVCSTL/include/ratio
    122 -    .../MSVCSTL/include/chrono
    121 -    ../llvm/include/llvm/Support/FormatVariadicDetails.h
    118 -    ../llvm/include/llvm/Support/MD5.h
    109 -    .../MSVCSTL/include/deque
    105 -    ../llvm/include/llvm/Support/Host.h
    105 -    ../llvm/include/llvm/Support/Endian.h

Reviewed By: aaron.ballman, hans

Differential Revision: https://reviews.llvm.org/D75279
2020-02-27 13:49:40 -08:00
Joe Turner b26c88e3c6 [clang-tidy] Store all ranges in clang::tooling::Diagnostic
Summary: Instead of dropping all the ranges associated with a Diagnostic when
converting them to a ClangTidy error, instead attach them to the ClangTidyError,
so they can be consumed by other APIs.

Patch by Joe Turner <joturner@google.com>.
Differential Revision: https://reviews.llvm.org/D69782
2020-02-27 19:39:42 +01:00
Haojian Wu aa324c5441 [clangd][NFC] Don't query the index if the rename symbol is function
local.

This would save an unnecessary index query when renaming a function
local symbol in cross-file rename mode.
2020-02-27 15:04:51 +01:00
Kadir Cetinkaya f31fc1043d
[clangd] Get rid of lexer usage in AST.cpp
Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75193
2020-02-27 09:54:21 +01:00
Kadir Cetinkaya 2bb7774ddf
[clangd] Get rid of getBeginningOfIdentifier helper
Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75176
2020-02-27 09:34:45 +01:00
Kadir Cetinkaya 2011d14296
[clangd] Clean-up XRefs.cpp from Lexer usages and unnecessary SourceLoc transformations
Summary:
Get rid of calls to lexer and unnecessary source location
transformations.

Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75166
2020-02-26 17:51:27 +01:00
Haojian Wu 02323a3d5f [clangd] use printQualifiedName to skip the inlinenamespace qualifiers.
Summary:
symbols in libcpp are inside the inline namespace, printQualifierAsString will
print the inline namespace, which is unexpected.

Reviewers: kadircet

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75174
2020-02-26 16:22:45 +01:00
Haojian Wu 5560a78820 [clangd] Bump index version number.
Summary:
Though we don't have new changes to the index format, we have changes to
symbol collector, e.g. collect marcos, spelled references. Bump the
version to force background-index to rebuild.

Reviewers: kadircet

Reviewed By: kadircet

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74127
2020-02-26 13:43:16 +01:00
Haojian Wu 4feca71df0 Fix the clangd-fuzzer build error. 2020-02-26 10:13:13 +01:00
Haojian Wu 34d0e1bd6d [clangd] Expose the rename LimitFiles option to the C++ API, NFC.
Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74834
2020-02-26 09:33:58 +01:00
Haojian Wu e6d0bad843 [clang-rename] Add the USR of incomplete decl to the USRSet.
Summary:
This fixes a clangd rename issue, which is missing the reference of
an incomplete specialization.

Unfortunately, I didn't reproduce this issue in clang-rename, I guess
the input `FoundDecl` of AdditionalUSRFinder is different in clangd vs
clang-rename, clang-rename uses the underlying CXXRecordDecl of the
ClassTemplateDecl, which is fixed in 5d862c042b;
while clangd-rename uses the ClassTemplateDecl.

Reviewers: kbobyrev

Reviewed By: kbobyrev

Subscribers: ilya-biryukov, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74829
2020-02-25 16:56:35 +01:00
Kadir Cetinkaya e09754ccef
[clangd] Migrate Lexer usages in TypeHierarchy to TokenBuffers
Summary:
Also fixes a bug, resulting from directly using ND.getEndLoc() for end
location of the range. As ND.getEndLoc() points to the begining of the last
token, whereas it should point one past the end, since LSP ranges are half open
(exclusive on the end).

Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74850
2020-02-25 15:36:45 +01:00
Kadir Cetinkaya 555d5ad85a
[clangd] Disable ExtractVariable for C
Summary:
Currently extract variable doesn't spell the type explicitly and just
uses an `auto` instead, which is not available in C.

Reviewers: usaxena95

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75053
2020-02-25 12:15:15 +01:00
Shoaib Meenai e34ddc09f4 [arcconfig] Delete subproject arcconfigs
From https://secure.phabricator.com/book/phabricator/article/arcanist_new_project/:

> An .arcconfig file is a JSON file which you check into your project's root.

I've done some experimentation, and it looks like the subproject
.arcconfigs just get ignored, as the documentation says. Given that
we're fully on the monorepo now, it's safe to remove them.

Differential Revision: https://reviews.llvm.org/D74996
2020-02-24 16:20:36 -08:00
Sam McCall e9997cfb4d [clangd] Try to fix buildbots - copy elision not happening here? 2020-02-23 21:12:26 +01:00
Sam McCall be6d07c920 [clangd] Reapply b60896fad9 Fall back to selecting token-before-cursor if token-after-cursor fails.
This reverts commit b4b9706d5d.
Now avoiding expected<vector<selection>> in favor of expected<vector<unique_ptr<selection>>>
2020-02-23 20:17:30 +01:00
Sam McCall b4b9706d5d Revert "[clangd] Reapply b60896fad9 Fall back to selecting token-before-cursor if token-after-cursor fails."
This reverts commit a2ce807eb7.

Buildbot failures on GCC due to SelectionTree not being copyable, and
instantiating vector<Selection> in the tweak-handling in ClangdServer.
2020-02-23 16:34:49 +01:00
Sam McCall a2ce807eb7 [clangd] Reapply b60896fad9 Fall back to selecting token-before-cursor if token-after-cursor fails.
This reverts commit 6af1ad20d6.
2020-02-23 16:17:46 +01:00
Sam McCall 7d3f8b1e2d [clangd] Debounce rebuilds responsively to rebuild times.
Summary:
Old: 500ms always. New: rebuild time, up to 500ms.

Fixes https://github.com/clangd/clangd/issues/275

Reviewers: hokein

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73949
2020-02-23 15:34:28 +01:00
Haojian Wu bc498198b5 [clangd] Allow renaming class templates in cross-file rename.
Summary:
It was disabled because we don't handle explicit template
specialization well (due to the index limitation).

renaming templates is normal in practic, rather than disabling it, this patch
allows to rename them though it is not perfect (just a known limitation).

Context: https://github.com/clangd/clangd/issues/280

Reviewers: kbobyrev

Reviewed By: kbobyrev

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74709
2020-02-21 09:57:10 +01:00
Haojian Wu e326f52430 [clangd] Fix the incomplete template specialization in findTarget.
Summary:
FindTarget doesn't report the TemplatePattern for incomplete
specialization.

Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74900
2020-02-21 09:42:02 +01:00
Eugene Zelenko db8911aad7 [clang-tidy] rename_check.py: maintain alphabetical order in Renamed checks section
Summary:
Also use //check// in add_new_check.py for terminology consistency.

PS

My GitHub ID is [[ https://github.com/EugeneZelenko | EugeneZelenko ]], if it's necessary for attribution.

Reviewers: alexfh, hokein, aaron.ballman, njames93, MyDeveloperDay

Reviewed By: njames93

Subscribers: Andi, xazax.hun, cfe-commits

Tags: #clang-tools-extra, #clang

Differential Revision: https://reviews.llvm.org/D73580
2020-02-20 17:31:08 +00:00
Haojian Wu bb9e92bad5 [clang][Index] Fix the incomplete instantiations in libindex.
Summary:
libindex will canonicalize references to template instantiations:
- 1) reference to an explicit template specialization, report the specializatiion
- 2) otherwise, report the primary template

but 2) is not true for incomplete instantiations, this patch fixes this.

Fixes https://github.com/clangd/clangd/issues/287

Reviewers: kadircet

Subscribers: ilya-biryukov, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74830
2020-02-20 14:42:30 +01:00
Roman Lebedev c8f9e526bc
[clang-tidy] misc-no-recursion: point to the function defs, not decls
Results in slightly better UX.
This actually was the initial intent, but it kinda got lost along the way.
2020-02-20 14:17:30 +03:00
Douglas Yung 6730f390a1 Fixup test after changes made in 709fd989.
The change added a test that required exceptions, so enable that explicitly
so that it works on platforms that default to having exceptions disabled
(like the PS4).
2020-02-19 18:39:54 -08:00
Nathan James d1d5180e69 [NFC] Fix issues with clang-tidy checks list.rst
Added FixItHint comments to ReservedIdentifierCheck and IdentifierNamingCheck to trick the python scripts into detecting a fix it is provided as it can't see the FixItHints in RenamerClangTidyCheck.cpp
2020-02-19 23:19:09 +00:00
Alexander Lanin 709fd989b6 [clang-tidy] fix readability-redundant-member-init auto-fix of Function-try-block
Summary: This fixes https://bugs.llvm.org/show_bug.cgi?id=39310

Reviewers: malcolm.parsons, ioeric

Reviewed By: malcolm.parsons

Subscribers: xazax.hun

Tags: #clang-format, #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D74800
2020-02-19 23:04:05 +00:00
Balázs Kéri fa6aef4427 [clang-tidy] Added a case to UnconventionalAssignOperatorCheck.
Summary:
The check accepts now a `return (*this = something);` as return
statement too (beneath of `*this`).

Reviewers: alexfh, hokein, aaron.ballman, JonasToth

Reviewed By: aaron.ballman

Subscribers: xazax.hun, dkrupp, Szelethus, gamesh411, cfe-commits

Tags: #clang, #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D74529
2020-02-19 10:07:34 +01:00
Kirill Bobyrev 4921e79192 Fix build after D74606 2020-02-19 09:19:15 +01:00
Kirill Bobyrev 2a095ff6f5
[clangd] Add add commit characters to the server capabilities
Summary:
Make it more convinient for the clients to select completion items by
providing a set of default characters (punctuation).

Related issue: https://github.com/clangd/clangd/issues/284

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74606
2020-02-19 08:32:00 +01:00
Eric Christopher 28728bf06f Fix a signed/unsigned warning promoted to error. 2020-02-18 17:49:22 -08:00
Karasev Nikita 47282b1b4b Fix PR#44620 'readability-redundant-string-cstr quick-fix causes invalid code'
static void f2(std::string&&) {}
static void f() {
	std::string const s;
	f2(s.c_str()); // readability-redundant-string-cstr previously warning
}

Skips the problematic AST pattern in the matcher.
2020-02-18 15:33:52 -05:00
Alexey Romanov 5e7d0ebf73 Cover cases like (b && c && b) in the redundant expression check.
readability-redundant-expression now detects expressions where a logical
or bitwise operator had equivalent LHS and RHS where the equivalent
operands were separated by more operands.
2020-02-18 11:42:32 -05:00
Gokturk Yuksek 351ed50dcb Reland "[clang-tools-extra] fix the check for if '-latomic' is necessary""
The buildbot failures on MSVC should have been fixed by f128f442a3.
2020-02-17 16:53:29 +00:00
Haojian Wu af8b0cd58d [clang][Index] Visit the default parameter arguements in libindex.
Summary:
We are missing the default parmeter arguments when IndexFunctionLocals
is true.

Fixes https://github.com/clangd/clangd/issues/285.

Reviewers: kadircet

Subscribers: kristof.beyls, ilya-biryukov, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74610
2020-02-17 16:45:04 +01:00
Benjamin Kramer 5fc5c7db38 Strength reduce vectors into arrays. NFCI. 2020-02-17 15:37:35 +01:00
Johannes Doerfert 803ad3137b [FIX] Repair clang-tidy check after D72304 2020-02-15 01:15:45 -06:00
Alexandre Ganea 8404aeb56a [Support] On Windows, ensure hardware_concurrency() extends to all CPU sockets and all NUMA groups
The goal of this patch is to maximize CPU utilization on multi-socket or high core count systems, so that parallel computations such as LLD/ThinLTO can use all hardware threads in the system. Before this patch, on Windows, a maximum of 64 hardware threads could be used at most, in some cases dispatched only on one CPU socket.

== Background ==
Windows doesn't have a flat cpu_set_t like Linux. Instead, it projects hardware CPUs (or NUMA nodes) to applications through a concept of "processor groups". A "processor" is the smallest unit of execution on a CPU, that is, an hyper-thread if SMT is active; a core otherwise. There's a limit of 32-bit processors on older 32-bit versions of Windows, which later was raised to 64-processors with 64-bit versions of Windows. This limit comes from the affinity mask, which historically is represented by the sizeof(void*). Consequently, the concept of "processor groups" was introduced for dealing with systems with more than 64 hyper-threads.

By default, the Windows OS assigns only one "processor group" to each starting application, in a round-robin manner. If the application wants to use more processors, it needs to programmatically enable it, by assigning threads to other "processor groups". This also means that affinity cannot cross "processor group" boundaries; one can only specify a "preferred" group on start-up, but the application is free to allocate more groups if it wants to.

This creates a peculiar situation, where newer CPUs like the AMD EPYC 7702P (64-cores, 128-hyperthreads) are projected by the OS as two (2) "processor groups". This means that by default, an application can only use half of the cores. This situation could only get worse in the years to come, as dies with more cores will appear on the market.

== The problem ==
The heavyweight_hardware_concurrency() API was introduced so that only *one hardware thread per core* was used. Once that API returns, that original intention is lost, only the number of threads is retained. Consider a situation, on Windows, where the system has 2 CPU sockets, 18 cores each, each core having 2 hyper-threads, for a total of 72 hyper-threads. Both heavyweight_hardware_concurrency() and hardware_concurrency() currently return 36, because on Windows they are simply wrappers over std:🧵:hardware_concurrency() -- which can only return processors from the current "processor group".

== The changes in this patch ==
To solve this situation, we capture (and retain) the initial intention until the point of usage, through a new ThreadPoolStrategy class. The number of threads to use is deferred as late as possible, until the moment where the std::threads are created (ThreadPool in the case of ThinLTO).

When using hardware_concurrency(), setting ThreadCount to 0 now means to use all the possible hardware CPU (SMT) threads. Providing a ThreadCount above to the maximum number of threads will have no effect, the maximum will be used instead.
The heavyweight_hardware_concurrency() is similar to hardware_concurrency(), except that only one thread per hardware *core* will be used.

When LLVM_ENABLE_THREADS is OFF, the threading APIs will always return 1, to ensure any caller loops will be exercised at least once.

Differential Revision: https://reviews.llvm.org/D71775
2020-02-14 10:24:22 -05:00
Luís Marques 13700c383f Revert "[clang-tools-extra] fix the check for if '-latomic' is necessary"
This reverts commit 1d40c41506.
This seemed to have caused build failures on ARM/AArch64.
2020-02-14 15:01:52 +00:00
Haojian Wu 5dc2314d5e [clangd] Update the CompletionItemKind.
Summary: Fix some FIXMEs.

Reviewers: kadircet

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74609
2020-02-14 15:48:30 +01:00
Haojian Wu 74c97ca1b4 [clangd] Add tracer to the rename workflow, NFC
Reviewers: kbobyrev

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74395
2020-02-14 15:39:29 +01:00
Gokturk Yuksek 1d40c41506 [clang-tools-extra] fix the check for if '-latomic' is necessary
Summary:
The CheckAtomic module performs two tests to determine if passing
'-latomic' to the linker is required: one for 64-bit atomics, and
another for non-64-bit atomics. clangd only uses the result from
HAVE_CXX_ATOMICS64_WITHOUT_LIB. This is incomplete because there are
uses of non-64-bit atomics in the code, such as the ReplyOnce::Replied
of type std::atomic<bool> defined in clangd/ClangdLSPServer.cpp.

Fix by also checking for the result of HAVE_CXX_ATOMICS_WITHOUT_LIB.

See also: https://reviews.llvm.org/D68964

Reviewers: ilya-biryukov, nridge, kadircet, beanz, compnerd, luismarques
Reviewed By: luismarques
Tags: #clang
Differential Revision: https://reviews.llvm.org/D69869
2020-02-14 14:16:10 +00:00
Kadir Cetinkaya 84240e0db8
[clang][Index] Introduce a TemplateParm SymbolKind
Summary:
Currently template parameters has symbolkind `Unknown`. This patch
introduces a new kind `TemplateParm` for templatetemplate, templatetype and
nontypetemplate parameters.

Also adds tests in clangd hover feature.

Reviewers: sammccall

Subscribers: kristof.beyls, ilya-biryukov, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73696
2020-02-14 13:20:34 +01:00
Kadir Cetinkaya c45fb35b5e
[clang][DeclPrinter] Implement visitors for {TemplateType,NonTypeTemplate}Parms
Reviewers: sammccall, hokein

Subscribers: kristof.beyls, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73693
2020-02-14 13:20:34 +01:00
Roman Lebedev b7d6640ba9
[NFC][clang-tidy] Move recently newly-added tests into checkers/ subdir
That's where nowadays those tests reside, those outliers were created
before the migration but committed after,
so they just awkwardly reside in the old place.
2020-02-14 11:25:05 +03:00
Roman Lebedev 49bffa5f8b
[clang-tidy] misc-no-recursion: a new check
Summary:
Recursion is a powerful tool, but like any tool
without care it can be dangerous. For example,
if the recursion is unbounded, you will
eventually run out of stack and crash.

You can of course track the recursion depth
but if it is hardcoded, there can always be some
other environment when that depth is too large,
so said magic number would need to be env-dependent.
But then your program's behavior is suddenly more env-dependent.

Also, recursion, while it does not outright stop optimization,
recursive calls are less great than normal calls,
for example they hinder inlining.

Recursion is banned in some coding guidelines:
* SEI CERT DCL56-CPP. Avoid cycles during initialization of static objects
* JPL 2.4 Do not use direct or indirect recursion.
* I'd say it is frowned upon in LLVM, although not banned
And is plain unsupported in some cases:
* OpenCL 1.2, 6.9 Restrictions: i. Recursion is not supported.

So there's clearly a lot of reasons why one might want to
avoid recursion, and replace it with worklist handling.
It would be great to have a enforcement for it though.

This implements such a check.
Here we detect both direct and indirect recursive calls,
although since clang-tidy (unlike clang static analyzer)
is CTU-unaware, if the recursion transcends a single standalone TU,
we will naturally not find it :/

The algorithm is pretty straight-forward:
1. Build call-graph for the entire TU.
   For that, the existing `clang::CallGraph` is re-used,
   although it had to be modified to also track the location of the call.
2. Then, the hard problem: how do we detect recursion?
   Since we have a graph, let's just do the sane thing,
   and look for Strongly Connected Function Declarations - widely known as `SCC`.
   For that LLVM provides `llvm::scc_iterator`,
   which is internally an Tarjan's DFS algorithm, and is used throught LLVM,
   so this should be as performant as possible.
3. Now that we've got SCC's, we discard those that don't contain loops.
   Note that there may be more than one loop in SCC!
4. For each loopy SCC, we call out each function, and print a single example
   call graph that shows recursion -- it didn't seem worthwhile enumerating
   every possible loop in SCC, although i suppose it could be implemented.
   * To come up with that call graph cycle example, we start at first SCC node,
     see which callee of the node is within SCC (and is thus known to be in cycle),
     and recurse into it until we hit the callee that is already in call stack.

Reviewers: JonasToth, aaron.ballman, ffrankies, Eugene.Zelenko, erichkeane, NoQ

Reviewed By: aaron.ballman

Subscribers: Charusso, Naghasan, bader, riccibruno, mgorny, Anastasia, xazax.hun, cfe-commits

Tags: #llvm, #clang

Differential Revision: https://reviews.llvm.org/D72362
2020-02-13 23:37:53 +03:00