[compiler-rt] [llvm] [asan] Limit priority of ctor to kMax-1 (PR #101772)

[Florian Mayer via llvm-commits]

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@@ -1993,6 +1994,29 @@ void ModuleAddressSanitizer::createInitializerPoisonCalls(
       poisonOneInitializer(*F, ModuleName);
     }
   }
+  assert(ClInitializers);
+  updateGlobalCtors(M, [](Constant *C) -> Constant * {
+    ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
+    if (!CS)
+      return C;
+    auto *Priority = cast<ConstantInt>(CS->getOperand(0));
+    if (Priority->getLimitedValue() != kMaxCtorAndDtorPriority)
+      return C;
+    // As optimization, runtime needs to execute callback just after all
+    // constructors. We going to set priority to the max allowed value. However,
+    // the default constructor priorily is already max, so as-is we will not be
+    // able to guaranty desired order. So reduce the priority by one to reserve
+    // max value for the constructor in runtime.
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fmayer wrote:

I will note that this could theoretically break user-code that depends on the order between `max` and `max-1`

https://github.com/llvm/llvm-project/pull/101772