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[clangd] Don't try pthread, just use thread_local. Reverts r323949. 

The pthread solution here breaks standalone builds, which don't have the
relevant cmake magic for feature-detection.

The original reason for trying pthread was fear of libgcc without
support for thread_local (e.g. on the clang-x86_64-linux-selfhost-modules bot).
However the earliest supported GCC is 4.8, and this has __cxa_thread_atexit.

This will probably break that bot, it's not running a supported GCC and needs
to be upgraded. I'll try to find out how to do this.

llvm-svn: 324351
This commit is contained in:
Sam McCall 2018-02-06 14:25:02 +00:00
parent 88f11003a0
commit 3aecc7fd45
1 changed files with 5 additions and 41 deletions
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46
clang-tools-extra/clangd/Context.cpp
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@ -8,49 +8,8 @@
//===---------------------------------------------------------------------===//
#include "Context.h"
#include "llvm/Config/config.h"
#include <cassert>
// The thread-local Context is scoped in a function to avoid init-order issues.
// It's created by currentContext() when first needed.
#ifdef HAVE_PTHREAD_GETSPECIFIC
// We'd love to use thread_local everywhere.
// It requires support from the runtime: __cxa_thread_atexit.
// Rather than detect this, we use the pthread API where available.
#include <pthread.h>
#include <cstring>
static clang::clangd::Context &currentContext() {
using clang::clangd::Context;
static pthread_key_t CtxKey;
// Once (across threads), set up pthread TLS for Context, and its destructor.
static int Dummy = [] { // Create key only once, for all threads.
if (auto Err = pthread_key_create(&CtxKey, /*destructor=*/+[](void *Ctx) {
delete reinterpret_cast<Context *>(Ctx);
}))
llvm_unreachable(strerror(Err));
return 0;
}();
(void)Dummy;
// Now grab the current context from TLS, and create it if it doesn't exist.
void *Ctx = pthread_getspecific(CtxKey);
if (!Ctx) {
Ctx = new Context();
if (auto Err = pthread_setspecific(CtxKey, Ctx))
llvm_unreachable(strerror(Err));
}
return *reinterpret_cast<Context *>(Ctx);
}
#else
// Only supported platform without pthread is windows, and thread_local works.
static clang::clangd::Context &currentContext() {
static thread_local auto C = clang::clangd::Context::empty();
return C;
}
#endif
namespace clang {
namespace clangd {
@ -61,6 +20,11 @@ Context::Context(std::shared_ptr<const Data> DataPtr)
Context Context::clone() const { return Context(DataPtr); }
static Context &currentContext() {
static thread_local auto C = Context::empty();
return C;
}
const Context &Context::current() { return currentContext(); }
Context Context::swapCurrent(Context Replacement) {