[lld] [llvm] [lld][AArch64][Build Attributes] Add support for converting AArch64 Build Attributes to GNU Properties (PR #131990)

[Peter Smith via llvm-commits]

================
@@ -207,6 +212,166 @@ static void updateSupportedARMFeatures(Ctx &ctx,
   ctx.arg.armHasThumb2ISA |= thumb && *thumb >= ARMBuildAttrs::AllowThumb32;
 }
 
+// Sanitize pauth values
+static void sanitizePauthSubSection(
+    Ctx &ctx, std::optional<llvm::BuildAttributeSubSection> &pauthSubSection,
+    InputSection isec) {
+  /*
+    Incomplete data: ignore
+  */
+  if (!pauthSubSection)
+    return;
+  // Currently there are 2 known tags defined for the pauth subsection,
+  // however, user is allowed to add other, unknown tag. If such tags exists,
+  // remove them. (no need to check for duplicates, they should not be possible)
+  pauthSubSection->Content.erase(
+      std::remove_if(pauthSubSection->Content.begin(),
+                     pauthSubSection->Content.end(),
+                     [](const BuildAttributeItem &item) {
+                       return item.Tag != 1 && item.Tag != 2;
+                     }),
+      pauthSubSection->Content.end());
+
+  if (pauthSubSection->Content.size() < 2) {
+    if (0 == pauthSubSection->Content.size())
----------------
smithp35 wrote:

`(0 == pauthSubSection->Content.size())` is not idiomatic for lld. While that way of writing if statements does have its advantages, it doesn't blend in with the rest of the lld code. While it will ultimately be up to MaskRay, I recommend using the form
`(pauthSubSection->Content.size() == 0)` or if there is a `.empty()` available then 
`(!pauthSubSection->empty())`

https://github.com/llvm/llvm-project/pull/131990