[ASan] Linker-initialize static ScopedInErrorReport::current_error_.

[alekseyshl]

Summary

Static ScopedInErrorReport::current_error_ can be linker initialized to
shave one global ctor call on application startup and be __asan_init-safe.

Global constructors in ASan runtime are bad because __asan_init runs
from preinit_array, before any such constructors.

Issue: https://github.com/google/sanitizers/issues/194

[delcypher]

Isn't this basically https://reviews.llvm.org/D44243 ?

[alekseyshl]

In D48141#1131507, @delcypher wrote:

Isn't this basically https://reviews.llvm.org/D44243 ?

It is! Thanks, missed that one. I'm fine with that one being committed too. Is the explanation on this patch satisfactory?

[delcypher]

In D48141#1131594, @alekseyshl wrote:

In D48141#1131507, @delcypher wrote:

Isn't this basically https://reviews.llvm.org/D44243 ?

It is! Thanks, missed that one. I'm fine with that one being committed too. Is the explanation on this patch satisfactory?

minor nit: s/on the startup/on application startup/ or s/on the startup/on startup/

I'm fine with either patch. My issue with D44243 is that the reason for the change wasn't provided. The explanation you provide was satisfactory once I read https://github.com/google/sanitizers/issues/194 .
Without reading the github issue it's not so clear what _asan_init-safe means. I'll leave it up to you to decide whether you want the commit message to be clear when read on its own or whether
referencing the GitHub issue is sufficient.

[alekseyshl]

In D48141#1132214, @delcypher wrote:

In D48141#1131594, @alekseyshl wrote:

In D48141#1131507, @delcypher wrote:

Isn't this basically https://reviews.llvm.org/D44243 ?

It is! Thanks, missed that one. I'm fine with that one being committed too. Is the explanation on this patch satisfactory?

minor nit: s/on the startup/on application startup/ or s/on the startup/on startup/

I'm fine with either patch. My issue with D44243 is that the reason for the change wasn't provided. The explanation you provide was satisfactory once I read https://github.com/google/sanitizers/issues/194 .
Without reading the github issue it's not so clear what _asan_init-safe means. I'll leave it up to you to decide whether you want the commit message to be clear when read on its own or whether
referencing the GitHub issue is sufficient.

Thank you for the suggestions, updated the message to provide a bit more inline context.

[filcab]

This got committed, but clang still warns:

/Users/filcab/dev/llvm/compiler-rt/lib/asan/asan_report.cc:209:39: warning: declaration requires a global constructor [-Wglobal-constructors]
ErrorDescription ScopedInErrorReport::current_error_(LINKER_INITIALIZED);
                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

compiler-rt/trunk/lib/asan/asan_errors.h

struct ErrorDescription {
   // We can add a wrapper around it to make it "more c++-like", but that would
   // add a lot of code and the benefit wouldn't be that big.
   union {
     ErrorBase Base;
     ASAN_FOR_EACH_ERROR_KIND(ASAN_ERROR_DESCRIPTION_MEMBER)
   };
 
   ErrorDescription() { internal_memset(this, 0, sizeof(*this)); }
+  explicit ErrorDescription(LinkerInitialized) {}
   ASAN_FOR_EACH_ERROR_KIND(ASAN_ERROR_DESCRIPTION_CONSTRUCTOR)
 
   bool IsValid() { return kind != kErrorKindInvalid; }
   void Print() {
     switch (kind) {
       ASAN_FOR_EACH_ERROR_KIND(ASAN_ERROR_DESCRIPTION_PRINT)
       case kErrorKindInvalid:
         CHECK(0);

compiler-rt/trunk/lib/asan/asan_report.cc

  private:
   ScopedErrorReportLock error_report_lock_;
   // Error currently being reported. This enables the destructor to interact
   // with the debugger and point it to an error description.
   static ErrorDescription current_error_;
   bool halt_on_error_;
 };
 
-ErrorDescription ScopedInErrorReport::current_error_;
+ErrorDescription ScopedInErrorReport::current_error_(LINKER_INITIALIZED);
 
 void ReportDeadlySignal(const SignalContext &sig) {
   ScopedInErrorReport in_report(/*fatal*/ true);
   ErrorDeadlySignal error(GetCurrentTidOrInvalid(), sig);
   in_report.ReportError(error);
 }
 
 void ReportDoubleFree(uptr addr, BufferedStackTrace *free_stack) {