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Clang doesn't have the same behavior as GCC does with union flexible
array members. (Technically, union FAMs are probably not acceptable in
C99 and are an extension / accidentally supported "feature" of GCC and
Clang, but I digress.)
Both Clang and GCC treat *all* arrays at the end of a structure as FAMs.
GCC does the same with unions. Clang does it for some arrays in unions
(incomplete, '0', and '1'), but for all. Instead of having this
half-supported feature, sync Clang's behavior with GCC's.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D135727
Files:
clang/lib/AST/Expr.cpp
clang/test/CodeGen/bounds-checking-fam.c
clang/test/CodeGen/bounds-checking.c
Index: clang/test/CodeGen/bounds-checking.c
===================================================================
--- clang/test/CodeGen/bounds-checking.c
+++ clang/test/CodeGen/bounds-checking.c
@@ -1,10 +1,10 @@
// RUN: %clang_cc1 -fsanitize=local-bounds -emit-llvm -triple x86_64-apple-darwin10 %s -o - | FileCheck %s
-// RUN: %clang_cc1 -fsanitize=array-bounds -O -fsanitize-trap=array-bounds -emit-llvm -triple x86_64-apple-darwin10 -DNO_DYNAMIC %s -o - | FileCheck %s --check-prefixes=CHECK,NONLOCAL
+// RUN: %clang_cc1 -fsanitize=array-bounds -O -fsanitize-trap=array-bounds -emit-llvm -triple x86_64-apple-darwin10 -DNO_DYNAMIC %s -o - | FileCheck %s
//
// REQUIRES: x86-registered-target
-// CHECK-LABEL: @f
-double f(int b, int i) {
+// CHECK-LABEL: @f1
+double f1(int b, int i) {
double a[b];
// CHECK: call {{.*}} @llvm.{{(ubsan)?trap}}
return a[i];
@@ -31,29 +31,38 @@
a[2] = 1;
}
+// CHECK-LABEL: @f4
+__attribute__((no_sanitize("bounds")))
+int f4(int i) {
+ int b[64];
+ // CHECK-NOT: call void @llvm.trap()
+ // CHECK-NOT: trap:
+ // CHECK-NOT: cont:
+ return b[i];
+}
+
+// Union flexible-array memebers are a C99 extension. All array members with a
+// constant size should be considered FAMs.
+
union U { int a[0]; int b[1]; int c[2]; };
-// CHECK-LABEL: define {{.*}} @f4
-int f4(union U *u, int i) {
- // a and b are treated as flexible array members.
- // CHECK-NOT: @llvm.ubsantrap
- return u->a[i] + u->b[i];
- // CHECK: }
-}
-
-// CHECK-LABEL: define {{.*}} @f5
+// CHECK-LABEL: @f5
int f5(union U *u, int i) {
- // c is not a flexible array member.
- // NONLOCAL: call {{.*}} @llvm.ubsantrap
- return u->c[i];
- // CHECK: }
+ // a is treated as a flexible array member.
+ // CHECK-NOT: @llvm.ubsantrap
+ return u->a[i];
}
-__attribute__((no_sanitize("bounds")))
-int f6(int i) {
- int b[64];
- // CHECK-NOT: call void @llvm.trap()
- // CHECK-NOT: trap:
- // CHECK-NOT: cont:
- return b[i];
+// CHECK-LABEL: @f6
+int f6(union U *u, int i) {
+ // b is treated as a flexible array member.
+ // CHECK-NOT: @llvm.ubsantrap
+ return u->b[i];
+}
+
+// CHECK-LABEL: @f7
+int f7(union U *u, int i) {
+ // c is treated as a flexible array member.
+ // CHECK-NOT: @llvm.ubsantrap
+ return u->c[i];
}
Index: clang/test/CodeGen/bounds-checking-fam.c
===================================================================
--- clang/test/CodeGen/bounds-checking-fam.c
+++ clang/test/CodeGen/bounds-checking-fam.c
@@ -1,14 +1,18 @@
// REQUIRES: x86-registered-target
-// RUN: %clang_cc1 -emit-llvm -triple x86_64 -fstrict-flex-arrays=0 -fsanitize=array-bounds %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-0
-// RUN: %clang_cc1 -emit-llvm -triple x86_64 -fstrict-flex-arrays=0 -fsanitize=array-bounds -x c++ %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-0,CXX,CXX-STRICT-0
-// RUN: %clang_cc1 -emit-llvm -triple x86_64 -fstrict-flex-arrays=1 -fsanitize=array-bounds %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-1
-// RUN: %clang_cc1 -emit-llvm -triple x86_64 -fstrict-flex-arrays=1 -fsanitize=array-bounds -x c++ %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-1,CXX
-// RUN: %clang_cc1 -emit-llvm -triple x86_64 -fstrict-flex-arrays=2 -fsanitize=array-bounds %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-2
-// RUN: %clang_cc1 -emit-llvm -triple x86_64 -fstrict-flex-arrays=2 -fsanitize=array-bounds -x c++ %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-2,CXX
+// RUN: %clang_cc1 -O2 -emit-llvm -triple x86_64 -fstrict-flex-arrays=0 -fsanitize=array-bounds %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-0
+// RUN: %clang_cc1 -O2 -emit-llvm -triple x86_64 -fstrict-flex-arrays=0 -fsanitize=array-bounds -x c++ %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-0,CXX,CXX-STRICT-0
+// RUN: %clang_cc1 -O2 -emit-llvm -triple x86_64 -fstrict-flex-arrays=1 -fsanitize=array-bounds %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-1
+// RUN: %clang_cc1 -O2 -emit-llvm -triple x86_64 -fstrict-flex-arrays=1 -fsanitize=array-bounds -x c++ %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-1,CXX
+// RUN: %clang_cc1 -O2 -emit-llvm -triple x86_64 -fstrict-flex-arrays=2 -fsanitize=array-bounds %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-2
+// RUN: %clang_cc1 -O2 -emit-llvm -triple x86_64 -fstrict-flex-arrays=2 -fsanitize=array-bounds -x c++ %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-STRICT-2,CXX
// Before flexible array member was added to C99, many projects use a
// one-element array as the last member of a structure as an alternative.
// E.g. https://github.com/python/cpython/issues/84301
// Suppress such errors with -fstrict-flex-arrays=0.
+
+union Zero {
+ int a[0];
+};
struct One {
int a[1];
};
@@ -19,6 +23,14 @@
int a[3];
};
+// CHECK-LABEL: define {{.*}} @{{.*}}test_zero{{.*}}(
+int test_zero(union Zero *p, int i) {
+ // CHECK-STRICT-0-NOT: @__ubsan
+ // CHECK-STRICT-1-NOT: @__ubsan
+ // CHECK-STRICT-2-NOT: @__ubsan
+ return p->a[i] + (p->a)[i];
+}
+
// CHECK-LABEL: define {{.*}} @{{.*}}test_one{{.*}}(
int test_one(struct One *p, int i) {
// CHECK-STRICT-0-NOT: @__ubsan
@@ -29,7 +41,15 @@
// CHECK-LABEL: define {{.*}} @{{.*}}test_two{{.*}}(
int test_two(struct Two *p, int i) {
- // CHECK-STRICT-0: call void @__ubsan_handle_out_of_bounds_abort(
+ // CHECK-STRICT-0-NOT: @__ubsan
+ // CHECK-STRICT-1: call void @__ubsan_handle_out_of_bounds_abort(
+ // CHECK-STRICT-2: call void @__ubsan_handle_out_of_bounds_abort(
+ return p->a[i] + (p->a)[i];
+}
+
+// CHECK-LABEL: define {{.*}} @{{.*}}test_three{{.*}}(
+int test_three(struct Three *p, int i) {
+ // CHECK-STRICT-0-NOT: @__ubsan
// CHECK-STRICT-1: call void @__ubsan_handle_out_of_bounds_abort(
// CHECK-STRICT-2: call void @__ubsan_handle_out_of_bounds_abort(
return p->a[i] + (p->a)[i];
@@ -60,29 +80,21 @@
int test_uone(union uOne *p, int i) {
// CHECK-STRICT-0-NOT: @__ubsan
// CHECK-STRICT-1-NOT: @__ubsan
- // CHECK-STRICT-2: @__ubsan
+ // CHECK-STRICT-2: call void @__ubsan_handle_out_of_bounds_abort(
return p->a[i] + (p->a)[i];
}
// CHECK-LABEL: define {{.*}} @{{.*}}test_utwo{{.*}}(
int test_utwo(union uTwo *p, int i) {
- // CHECK-STRICT-0: @__ubsan
- // CHECK-STRICT-1: @__ubsan
- // CHECK-STRICT-2: @__ubsan
+ // CHECK-STRICT-0-NOT: @__ubsan
+ // CHECK-STRICT-1: call void @__ubsan_handle_out_of_bounds_abort(
+ // CHECK-STRICT-2: call void @__ubsan_handle_out_of_bounds_abort(
return p->a[i] + (p->a)[i];
}
// CHECK-LABEL: define {{.*}} @{{.*}}test_uthree{{.*}}(
int test_uthree(union uThree *p, int i) {
- // CHECK-STRICT-0: @__ubsan
- // CHECK-STRICT-1: @__ubsan
- // CHECK-STRICT-2: @__ubsan
- return p->a[i] + (p->a)[i];
-}
-
-// CHECK-LABEL: define {{.*}} @{{.*}}test_three{{.*}}(
-int test_three(struct Three *p, int i) {
- // CHECK-STRICT-0: call void @__ubsan_handle_out_of_bounds_abort(
+ // CHECK-STRICT-0-NOT: @__ubsan
// CHECK-STRICT-1: call void @__ubsan_handle_out_of_bounds_abort(
// CHECK-STRICT-2: call void @__ubsan_handle_out_of_bounds_abort(
return p->a[i] + (p->a)[i];
Index: clang/lib/AST/Expr.cpp
===================================================================
--- clang/lib/AST/Expr.cpp
+++ clang/lib/AST/Expr.cpp
@@ -207,7 +207,6 @@
ASTContext &Context,
LangOptions::StrictFlexArraysLevelKind StrictFlexArraysLevel,
bool IgnoreTemplateOrMacroSubstitution) const {
-
// For compatibility with existing code, we treat arrays of length 0 or
// 1 as flexible array members.
if (const auto *CAT = Context.getAsConstantArrayType(getType())) {
@@ -217,13 +216,16 @@
if (Size == 0)
return true;
+ using FAMKind = LangOptions::StrictFlexArraysLevelKind;
+
// FIXME: While the default -fstrict-flex-arrays=0 permits Size>1 trailing
// arrays to be treated as flexible-array-members, we still emit diagnostics
// as if they are not. Pending further discussion...
- using FAMKind = LangOptions::StrictFlexArraysLevelKind;
- if (StrictFlexArraysLevel == FAMKind::ZeroOrIncomplete || Size.uge(2))
+ if (StrictFlexArraysLevel == FAMKind::ZeroOrIncomplete && Size.uge(1))
return false;
+ if (StrictFlexArraysLevel == FAMKind::OneZeroOrIncomplete && Size.uge(2))
+ return false;
} else if (!Context.getAsIncompleteArrayType(getType()))
return false;
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