[-Wunsafe-buffer-usage] Add absl::{Span,string_view} to UnsafeBufferUsage analysis

[mxms0]

Add support for absl Span and string_view types to warn on their unsafe usage.

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[llvmbot]

@llvm/pr-subscribers-clang

Author: Max (mxms0)

Changes

Add support for absl Span and string_view types to warn on their unsafe usage.

---

Full diff: https://github.com/llvm/llvm-project/pull/127698.diff

1 Files Affected:

• (modified) clang/lib/Analysis/UnsafeBufferUsage.cpp (+3-1)

diff --git a/clang/lib/Analysis/UnsafeBufferUsage.cpp b/clang/lib/Analysis/UnsafeBufferUsage.cpp
index c51398698922b..e0f9a683bdb6c 100644
--- a/clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ b/clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -891,7 +891,9 @@ AST_MATCHER(CallExpr, hasUnsafeSnprintfBuffer) {
 
   // Pattern 1:
   static StringRef SizedObjs[] = {"span", "array", "vector",
-                                  "basic_string_view", "basic_string"};
+                                  "basic_string_view", "basic_string",
+                                   // Support absl::Span and absl::string_view
+                                  "Span", "string_view" };
   Buf = Buf->IgnoreParenImpCasts();
   Size = Size->IgnoreParenImpCasts();
   if (auto *MCEPtr = dyn_cast<CXXMemberCallExpr>(Buf))

[llvmbot]

@llvm/pr-subscribers-clang-analysis

Author: Max (mxms0)

Changes

Add support for absl Span and string_view types to warn on their unsafe usage.

---

Full diff: https://github.com/llvm/llvm-project/pull/127698.diff

1 Files Affected:

• (modified) clang/lib/Analysis/UnsafeBufferUsage.cpp (+3-1)

diff --git a/clang/lib/Analysis/UnsafeBufferUsage.cpp b/clang/lib/Analysis/UnsafeBufferUsage.cpp
index c51398698922b..e0f9a683bdb6c 100644
--- a/clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ b/clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -891,7 +891,9 @@ AST_MATCHER(CallExpr, hasUnsafeSnprintfBuffer) {
 
   // Pattern 1:
   static StringRef SizedObjs[] = {"span", "array", "vector",
-                                  "basic_string_view", "basic_string"};
+                                  "basic_string_view", "basic_string",
+                                   // Support absl::Span and absl::string_view
+                                  "Span", "string_view" };
   Buf = Buf->IgnoreParenImpCasts();
   Size = Size->IgnoreParenImpCasts();
   if (auto *MCEPtr = dyn_cast<CXXMemberCallExpr>(Buf))

[mxms0]

cc @jkorous-apple

[ilya-biryukov]

This makes sense, although I suspect it doesn't work because the code checks for std namespace.

It would be nice to get a signal from the code owners that they're happy with adding Abseil as a special case in addition to STL. Hopefully it's a no-brainer as it's coming from Googlers, who are owners of Abseil.

Could you also add a test? (search for Wunsafe-buffer-usage inside clang/test if you need existing examples)

[ilya-biryukov]

I am afraid this will not work because of the following check on line 920:

          if (MCEPtr->getRecordDecl()->isInStdNamespace() &&
              MCEPtr->getRecordDecl()->getCanonicalDecl()->getName() ==
                  SizedObj)

You want to change this to take namespace into account somehow. I suggest creating a method IsInNamedNamespace that accepts the namespace name and passes it all the way down to this function that current passes a string constant "std".

llvm-project/clang/lib/AST/DeclBase.cpp

Line 1344 in 3dc1594

return II && II->isStr("std");

That way the IsInStdNamespace will be implemented as return IsInNamedNamespace("std")

PS a more sophisticated version would allow to follow multiple nested namespaces is probably also useful, but I'd not bother with it for now.

[ziqingluo-90]

yes, please match namespaces. It also helps preventing false negatives. You probably do not want to match any type named Span.

[malavikasamak]

I agree. We need name space checks here.

[jkorous-apple]

+1 for tests