[clang] Control analysis-based diagnostics with #pragma (PR #136323)

[Erich Keane via cfe-commits]

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@@ -202,6 +202,43 @@ class SemaPPCallbacks : public PPCallbacks {
       break;
     }
   }
+  void PragmaDiagnostic(SourceLocation Loc, StringRef Namespace,
+                        diag::Severity Mapping, StringRef Str) override {
+    // If one of the analysis-based diagnostics was enabled while processing
+    // a function, we want to note it in the analysis-based warnings so they
+    // can be run at the end of the function body even if the analysis warnings
+    // are disabled at that point.
+    SmallVector<diag::kind, 256> GroupDiags;
+    diag::Flavor Flavor =
+        Str[1] == 'W' ? diag::Flavor::WarningOrError : diag::Flavor::Remark;
+    StringRef Group = Str.substr(2);
+
+    if (S->PP.getDiagnostics().getDiagnosticIDs()->getDiagnosticsInGroup(
+            Flavor, Group, GroupDiags))
+      return;
+
+    for (diag::kind K : GroupDiags) {
+      // Note: the cases in this switch should be kept in sync with the
+      // diagnostics in AnalysisBasedWarnings::getPolicyInEffectAt().
+      AnalysisBasedWarnings::Policy &Override =
+          S->AnalysisWarnings.getPolicyOverrides();
+      switch (K) {
+      default: break;
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erichkeane wrote:

At the moment, yes.  As a follow-up, I would wonder if we could auto-generate this from tablegen.  

Though, in this patch, we could perhaps instead of doing this override, have the policy store a LIST of override diagnostics, that we then check are in the list.  So this would instead of this whole switch do:

`Override.DiagOverrideList.push_back(K);`

That would work for ALL diagnostics, at the expense of a somewhat significant size increase.

https://github.com/llvm/llvm-project/pull/136323