From 42f588f39c5ce6f521e3709b8871d1fdd076292f Mon Sep 17 00:00:00 2001
From: Mehdi Amini <joker.eph@gmail.com>
Date: Thu, 15 Jul 2021 23:52:44 +0000
Subject: Use ManagedStatic and lazy initialization of cl::opt in libSupport to
 make it free of global initializer

We can build it with -Werror=global-constructors now. This helps
in situation where libSupport is embedded as a shared library,
potential with dlopen/dlclose scenario, and when command-line
parsing or other facilities may not be involved. Avoiding the
implicit construction of these cl::opt can avoid double-registration
issues and other kind of behavior.

Reviewed By: lattner, jpienaar

Differential Revision: https://reviews.llvm.org/D105959
---
 llvm/lib/Support/Debug.cpp | 73 +++++++++++++++++++++++++++++++++-------------
 1 file changed, 52 insertions(+), 21 deletions(-)

(limited to 'llvm/lib/Support/Debug.cpp')

diff --git a/llvm/lib/Support/Debug.cpp b/llvm/lib/Support/Debug.cpp
index 19b40ab..b48045c 100644
--- a/llvm/lib/Support/Debug.cpp
+++ b/llvm/lib/Support/Debug.cpp
@@ -30,6 +30,8 @@
 #include "llvm/Support/circular_raw_ostream.h"
 #include "llvm/Support/raw_ostream.h"
 
+#include "DebugOptions.h"
+
 #undef isCurrentDebugType
 #undef setCurrentDebugType
 #undef setCurrentDebugTypes
@@ -79,21 +81,32 @@ void setCurrentDebugTypes(const char **Types, unsigned Count) {
 // All Debug.h functionality is a no-op in NDEBUG mode.
 #ifndef NDEBUG
 
-// -debug - Command line option to enable the DEBUG statements in the passes.
-// This flag may only be enabled in debug builds.
-static cl::opt<bool, true>
-Debug("debug", cl::desc("Enable debug output"), cl::Hidden,
-      cl::location(DebugFlag));
+namespace {
+struct CreateDebug {
+  static void *call() {
+    return new cl::opt<bool, true>("debug", cl::desc("Enable debug output"),
+                                   cl::Hidden, cl::location(DebugFlag));
+  }
+};
 
 // -debug-buffer-size - Buffer the last N characters of debug output
 //until program termination.
-static cl::opt<unsigned>
-DebugBufferSize("debug-buffer-size",
-                cl::desc("Buffer the last N characters of debug output "
-                         "until program termination. "
-                         "[default 0 -- immediate print-out]"),
-                cl::Hidden,
-                cl::init(0));
+struct CreateDebugBufferSize {
+  static void *call() {
+    return new cl::opt<unsigned>(
+        "debug-buffer-size",
+        cl::desc("Buffer the last N characters of debug output "
+                 "until program termination. "
+                 "[default 0 -- immediate print-out]"),
+        cl::Hidden, cl::init(0));
+  }
+};
+} // namespace
+
+// -debug - Command line option to enable the DEBUG statements in the passes.
+// This flag may only be enabled in debug builds.
+static ManagedStatic<cl::opt<bool, true>, CreateDebug> Debug;
+static ManagedStatic<cl::opt<unsigned>, CreateDebugBufferSize> DebugBufferSize;
 
 namespace {
 
@@ -108,15 +121,33 @@ struct DebugOnlyOpt {
       CurrentDebugType->push_back(std::string(dbgType));
   }
 };
-
 } // namespace
 
 static DebugOnlyOpt DebugOnlyOptLoc;
 
-static cl::opt<DebugOnlyOpt, true, cl::parser<std::string> >
-DebugOnly("debug-only", cl::desc("Enable a specific type of debug output (comma separated list of types)"),
-          cl::Hidden, cl::ZeroOrMore, cl::value_desc("debug string"),
-          cl::location(DebugOnlyOptLoc), cl::ValueRequired);
+namespace {
+struct CreateDebugOnly {
+  static void *call() {
+    return new cl::opt<DebugOnlyOpt, true, cl::parser<std::string>>(
+        "debug-only",
+        cl::desc("Enable a specific type of debug output (comma separated list "
+                 "of types)"),
+        cl::Hidden, cl::ZeroOrMore, cl::value_desc("debug string"),
+        cl::location(DebugOnlyOptLoc), cl::ValueRequired);
+  }
+};
+} // namespace
+
+static ManagedStatic<cl::opt<DebugOnlyOpt, true, cl::parser<std::string>>,
+                     CreateDebugOnly>
+    DebugOnly;
+
+void llvm::initDebugOptions() {
+  *Debug;
+  *DebugBufferSize;
+  *DebugOnly;
+}
+
 // Signal handlers - dump debug output on termination.
 static void debug_user_sig_handler(void *Cookie) {
   // This is a bit sneaky.  Since this is under #ifndef NDEBUG, we
@@ -134,10 +165,10 @@ raw_ostream &llvm::dbgs() {
   static struct dbgstream {
     circular_raw_ostream strm;
 
-    dbgstream() :
-        strm(errs(), "*** Debug Log Output ***\n",
-             (!EnableDebugBuffering || !DebugFlag) ? 0 : DebugBufferSize) {
-      if (EnableDebugBuffering && DebugFlag && DebugBufferSize != 0)
+    dbgstream()
+        : strm(errs(), "*** Debug Log Output ***\n",
+               (!EnableDebugBuffering || !DebugFlag) ? 0 : *DebugBufferSize) {
+      if (EnableDebugBuffering && DebugFlag && *DebugBufferSize != 0)
         // TODO: Add a handler for SIGUSER1-type signals so the user can
         // force a debug dump.
         sys::AddSignalHandler(&debug_user_sig_handler, nullptr);
-- 
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