[PATCH] D23385: Implement __attribute__((require_constant_initialization)) for safe static initialization.

[Eric Fiselier via cfe-commits]

EricWF added inline comments.

================
Comment at: lib/Sema/SemaDecl.cpp:10484-10485
@@ -10478,1 +10483,4 @@
 
+  if (var->hasAttr<RequireConstantInitAttr>() && !Init)
+     Diag(var->getLocation(), diag::err_require_constant_init_failed);
+
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rsmith wrote:
> I think this check is incorrect: we perform constant initialization (to zero) for globals with no initializer.
Agreed. Technically not "constant initialization" but every bit as safe.

================
Comment at: lib/Sema/SemaDecl.cpp:10485
@@ +10484,3 @@
+  if (var->hasAttr<RequireConstantInitAttr>() && !Init)
+     Diag(var->getLocation(), diag::err_require_constant_init_failed);
+
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majnemer wrote:
> Any reason not to use the already existing `err_init_element_not_constant`?
> Any reason not to use the already existing err_init_element_not_constant?

I hadn't considered it, but the error text seems misleading, since it may select a constructor that's not a valid constant expression even when every element in the initializer is.

================
Comment at: lib/Sema/SemaDecl.cpp:10500
@@ +10499,3 @@
+        if (!*HasConstInit)
+          Diag(var->getLocation(), diag::warn_global_constructor)
+            << Init->getSourceRange();
----------------
rsmith wrote:
> Instead of diagnosing the condition separately (and getting both a warning and an error for the same situation), it would seem preferable to change this to produce either `diag::warn_global_constructor` or your new error depending on whether the attribute is present. This would also remove the duplicate error messages if the attribute is specified on an object that is also marked `constexpr`.
Already I think I've dealt with the duplicate diagnostics.

================
Comment at: lib/Sema/SemaDecl.cpp:10528
@@ +10527,3 @@
+                                    var->getLocation())) {
+      // Warn about globals which don't have a constant initializer.  Don't
+      // warn about globals with a non-trivial destructor because we already
----------------
I can't figure out where the diagnostic is this comment is coming from. Hopefully I'm just missing something simple.


https://reviews.llvm.org/D23385