[clang] [Clang] Diagnose nested inline asm variants (PR #232686)
Shray Jaiswal via cfe-commits
cfe-commits at lists.llvm.org
Fri Oct 16 04:10:43 PDT 2026
https://github.com/shrayjaiswal050-design created https://github.com/llvm/llvm-project/pull/232686
Fixes #232406
Clang currently accepts nested GCC inline-assembly dialect variants and
later crashes in the backend. Diagnose nested variants during Sema instead.
Testing:
- i686 and x86-64 Sema -verify tests
- Valid inline-asm output-variant codegen test
- Reduced Clang build: 572/572 targets
- Original reproducer now emits the diagnostic instead of crashing
>From 4d88efa98053905a3b26e89f596af6707a0216a4 Mon Sep 17 00:00:00 2001
From: shrayjaiswal050-design <shray.jaiswal050 at gmail.com>
Date: Fri, 16 Oct 2026 16:22:11 +0530
Subject: [PATCH 1/2] [Clang] Diagnose nested inline asm variants
---
clang/include/clang/Basic/DiagnosticASTKinds.td | 2 ++
clang/lib/AST/Stmt.cpp | 15 +++++++++++++--
clang/test/Sema/inline-asm-validate-x86.c | 4 ++++
3 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/clang/include/clang/Basic/DiagnosticASTKinds.td b/clang/include/clang/Basic/DiagnosticASTKinds.td
index 48241ebe5c3dcb..d059835a636f5d 100644
--- a/clang/include/clang/Basic/DiagnosticASTKinds.td
+++ b/clang/include/clang/Basic/DiagnosticASTKinds.td
@@ -454,6 +454,8 @@ def err_invalid_is_within_lifetime : Note<
let CategoryName = "Inline Assembly Issue" in {
def err_asm_invalid_escape : Error<
"invalid %% escape in inline assembly string">;
+ def err_asm_nested_variant : Error<
+ "nested variants found in inline assembly string">;
def err_asm_unknown_symbolic_operand_name : Error<
"unknown symbolic operand name in inline assembly string">;
diff --git a/clang/lib/AST/Stmt.cpp b/clang/lib/AST/Stmt.cpp
index 15d0e6435aaf3a..51c9ea86725967 100644
--- a/clang/lib/AST/Stmt.cpp
+++ b/clang/lib/AST/Stmt.cpp
@@ -698,6 +698,7 @@ unsigned GCCAsmStmt::AnalyzeAsmString(SmallVectorImpl<AsmStringPiece>&Pieces,
std::string CurStringPiece;
bool HasVariants = !C.getTargetInfo().hasNoAsmVariants();
+ bool InVariant = false;
unsigned LastAsmStringToken = 0;
unsigned LastAsmStringOffset = 0;
@@ -713,9 +714,19 @@ unsigned GCCAsmStmt::AnalyzeAsmString(SmallVectorImpl<AsmStringPiece>&Pieces,
char CurChar = *CurPtr++;
switch (CurChar) {
case '$': CurStringPiece += "$$"; continue;
- case '{': CurStringPiece += (HasVariants ? "$(" : "{"); continue;
+ case '{':
+ if (HasVariants && InVariant) {
+ DiagOffs = CurPtr - StrStart - 1;
+ return diag::err_asm_nested_variant;
+ }
+ CurStringPiece += (HasVariants ? "$(" : "{");
+ InVariant = HasVariants;
+ continue;
case '|': CurStringPiece += (HasVariants ? "$|" : "|"); continue;
- case '}': CurStringPiece += (HasVariants ? "$)" : "}"); continue;
+ case '}':
+ CurStringPiece += (HasVariants ? "$)" : "}");
+ InVariant = false;
+ continue;
case '%':
break;
default:
diff --git a/clang/test/Sema/inline-asm-validate-x86.c b/clang/test/Sema/inline-asm-validate-x86.c
index d4c10c36f5fbea..c44c534ff8fd1d 100644
--- a/clang/test/Sema/inline-asm-validate-x86.c
+++ b/clang/test/Sema/inline-asm-validate-x86.c
@@ -138,3 +138,7 @@ void test_W(int i) {
// Codegen error
__asm__("" : : "Ws"(i));
}
+
+void test_nested_variants(long num) {
+ __asm__("{{movq $42, %0|}" : "=r"(num)); // expected-error{{nested variants found in inline assembly string}}
+}
>From 12580ad9e32ca23162ebdbb08586f23d209ff133 Mon Sep 17 00:00:00 2001
From: shrayjaiswal050-design <shray.jaiswal050 at gmail.com>
Date: Fri, 16 Oct 2026 16:22:11 +0530
Subject: [PATCH 2/2] [Clang] Diagnose nested inline asm variants
---
clang/include/clang/Basic/DiagnosticASTKinds.td | 2 ++
clang/lib/AST/Stmt.cpp | 15 +++++++++++++--
clang/test/Sema/inline-asm-validate-x86.c | 4 ++++
3 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/clang/include/clang/Basic/DiagnosticASTKinds.td b/clang/include/clang/Basic/DiagnosticASTKinds.td
index 48241ebe5c3dcb..d059835a636f5d 100644
--- a/clang/include/clang/Basic/DiagnosticASTKinds.td
+++ b/clang/include/clang/Basic/DiagnosticASTKinds.td
@@ -454,6 +454,8 @@ def err_invalid_is_within_lifetime : Note<
let CategoryName = "Inline Assembly Issue" in {
def err_asm_invalid_escape : Error<
"invalid %% escape in inline assembly string">;
+ def err_asm_nested_variant : Error<
+ "nested variants found in inline assembly string">;
def err_asm_unknown_symbolic_operand_name : Error<
"unknown symbolic operand name in inline assembly string">;
diff --git a/clang/lib/AST/Stmt.cpp b/clang/lib/AST/Stmt.cpp
index 15d0e6435aaf3a..51c9ea86725967 100644
--- a/clang/lib/AST/Stmt.cpp
+++ b/clang/lib/AST/Stmt.cpp
@@ -698,6 +698,7 @@ unsigned GCCAsmStmt::AnalyzeAsmString(SmallVectorImpl<AsmStringPiece>&Pieces,
std::string CurStringPiece;
bool HasVariants = !C.getTargetInfo().hasNoAsmVariants();
+ bool InVariant = false;
unsigned LastAsmStringToken = 0;
unsigned LastAsmStringOffset = 0;
@@ -713,9 +714,19 @@ unsigned GCCAsmStmt::AnalyzeAsmString(SmallVectorImpl<AsmStringPiece>&Pieces,
char CurChar = *CurPtr++;
switch (CurChar) {
case '$': CurStringPiece += "$$"; continue;
- case '{': CurStringPiece += (HasVariants ? "$(" : "{"); continue;
+ case '{':
+ if (HasVariants && InVariant) {
+ DiagOffs = CurPtr - StrStart - 1;
+ return diag::err_asm_nested_variant;
+ }
+ CurStringPiece += (HasVariants ? "$(" : "{");
+ InVariant = HasVariants;
+ continue;
case '|': CurStringPiece += (HasVariants ? "$|" : "|"); continue;
- case '}': CurStringPiece += (HasVariants ? "$)" : "}"); continue;
+ case '}':
+ CurStringPiece += (HasVariants ? "$)" : "}");
+ InVariant = false;
+ continue;
case '%':
break;
default:
diff --git a/clang/test/Sema/inline-asm-validate-x86.c b/clang/test/Sema/inline-asm-validate-x86.c
index d4c10c36f5fbea..c44c534ff8fd1d 100644
--- a/clang/test/Sema/inline-asm-validate-x86.c
+++ b/clang/test/Sema/inline-asm-validate-x86.c
@@ -138,3 +138,7 @@ void test_W(int i) {
// Codegen error
__asm__("" : : "Ws"(i));
}
+
+void test_nested_variants(long num) {
+ __asm__("{{movq $42, %0|}" : "=r"(num)); // expected-error{{nested variants found in inline assembly string}}
+}
More information about the cfe-commits
mailing list