[clang] [WIP][DO NOT MERGE][Clang][Driver] Emit warning when -fsanitize-trap=<...> is passed without associated -fsanitize=<...> (PR #147997)

[Anthony Tran via cfe-commits]

https://github.com/anthonyhatran updated https://github.com/llvm/llvm-project/pull/147997

>From eadf3e52072fbae01e8de8f7f59883aec1b2c9bc Mon Sep 17 00:00:00 2001
From: Anthony Tran <anthonytran at anthonys-air.lan>
Date: Thu, 10 Jul 2025 09:18:50 -0700
Subject: [PATCH 1/3] Added warning and warning group for sanitizer argument
 mismatch

---
 clang/include/clang/Basic/DiagnosticDriverKinds.td | 5 +++++
 clang/include/clang/Basic/DiagnosticGroups.td      | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 34b6c0d7a8acd..49a8bdf06bda4 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -874,4 +874,9 @@ def warn_drv_openacc_without_cir
     : Warning<"OpenACC directives will result in no runtime behavior; use "
               "-fclangir to enable runtime effect">,
       InGroup<SourceUsesOpenACC>;
+
+def warn_drv_sanitize_trap_mismatch : Warning<
+  "-fsanitize-trap=%0 has no effect because the matching sanitizer is not enabled; "
+  "did you mean to pass \"-fsanitize=%0\" as well?">,
+  InGroup<SanitizeTrapMismatch>;
 }
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index f54a830b0103e..a79562cd9c2e0 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -1752,3 +1752,6 @@ def ExplicitSpecializationStorageClass : DiagGroup<"explicit-specialization-stor
 
 // A warning for options that enable a feature that is not yet complete
 def ExperimentalOption : DiagGroup<"experimental-option">;
+
+// Warnings for sanitizer arguments
+def SanitizeTrapMismatch : DiagGroup<"sanitize-trap-mismatch">;

>From f1bf9b34daca5d23d1a3f518847f3ccbc8f069a7 Mon Sep 17 00:00:00 2001
From: Anthony Tran <anthonytran at anthonys-air.lan>
Date: Thu, 10 Jul 2025 13:35:52 -0700
Subject: [PATCH 2/3] Emit warning and parse mismatched arguments

---
 clang/lib/Driver/SanitizerArgs.cpp | 36 ++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index 4bd61c2f8deef..8b78d850e0018 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -348,6 +348,30 @@ parseSanitizeSkipHotCutoffArgs(const Driver &D, const llvm::opt::ArgList &Args,
   return Cutoffs;
 }
 
+// Given a set of mismatched bits, TrapOnly (bits the user asked to trap but
+// that aren’t actually enabled), emit a warning based on -fsanitize-trap=NAME
+static void diagnoseTrapOnly(const Driver &D, SanitizerMask &TrapOnly) {
+// Double pass: one for sanitizer groupings, one for leaves (ex: undefined vs.
+// signed-integer-overflow)
+#define SANITIZER(NAME, ID)
+#define SANITIZER_GROUP(NAME, ID, ALIAS)                                       \
+  if (TrapOnly & SanitizerKind::ID##Group) {                                   \
+    D.Diag(diag::warn_drv_sanitize_trap_mismatch) << NAME;                     \
+    TrapOnly &= ~SanitizerKind::ID##Group;                                     \
+    TrapOnly &= ~SanitizerKind::ID;                                            \
+  }
+#include "clang/Basic/Sanitizers.def"
+
+#undef SANITIZER_GROUP
+#define SANITIZER_GROUP(NAME, ID, ALIAS)
+#define SANITIZER(NAME, ID)                                                    \
+  if (TrapOnly & SanitizerKind::ID) {                                          \
+    D.Diag(diag::warn_drv_sanitize_trap_mismatch) << NAME;                     \
+    TrapOnly &= ~SanitizerKind::ID;                                            \
+  }
+#include "clang/Basic/Sanitizers.def"
+}
+
 bool SanitizerArgs::needsFuzzerInterceptors() const {
   return needsFuzzer() && !needsAsanRt() && !needsTsanRt() && !needsMsanRt();
 }
@@ -730,6 +754,18 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
       options::OPT_fno_sanitize_recover_EQ);
   RecoverableKinds &= Kinds;
 
+  // Parse any -fsanitize-trap=<...> flags the user provided, then
+  // diagnose any which do not have a matching -fsanitize=<...>
+  if (DiagnoseErrors) {
+    SanitizerMask ExplicitTrap = parseSanitizeArgs(
+        D, Args, false, {}, {}, {}, options::OPT_fsanitize_trap_EQ,
+        options::OPT_fno_sanitize_trap_EQ);
+    SanitizerMask TrapOnly = ExplicitTrap & ~Kinds;
+
+    if (TrapOnly)
+      diagnoseTrapOnly(D, TrapOnly);
+  }
+
   TrappingKinds &= Kinds;
   RecoverableKinds &= ~TrappingKinds;
 

>From c7b44099357ee78329f6e289ef6feb321b9b121c Mon Sep 17 00:00:00 2001
From: Anthony Tran <anthonytran at anthonys-air.lan>
Date: Mon, 14 Jul 2025 03:36:11 -0700
Subject: [PATCH 3/3] Modify warning message

---
 clang/include/clang/Basic/DiagnosticDriverKinds.td | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 49a8bdf06bda4..f2a0582a364bf 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -876,7 +876,7 @@ def warn_drv_openacc_without_cir
       InGroup<SourceUsesOpenACC>;
 
 def warn_drv_sanitize_trap_mismatch : Warning<
-  "-fsanitize-trap=%0 has no effect because the matching sanitizer is not enabled; "
-  "did you mean to pass \"-fsanitize=%0\" as well?">,
+  "-fsanitize-trap=%0 has no effect because the \"%0\" sanitizer is disabled; "
+  "consider passing \"fsanitize=%0\" to enable the sanitizer">,
   InGroup<SanitizeTrapMismatch>;
 }