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7f93ae8086
The -fstrict-flex-arrays=3 is the most restrictive type of flex arrays.
No number, including 0, is allowed in the FAM. In the cases where a "0"
is used, the resulting size is the same as if a zero-sized object were
substituted.
This is needed for proper _FORTIFY_SOURCE coverage in the Linux kernel,
among other reasons. So while the only reason for specifying a
zero-length array at the end of a structure is for specify a FAM,
treating it as such will cause _FORTIFY_SOURCE not to work correctly;
__builtin_object_size will report -1 instead of 0 for a destination
buffer size to keep any kernel internals from using the deprecated
members as fake FAMs.
For example:
struct broken {
int foo;
int fake_fam[0];
struct something oops;
};
There have been bugs where the above struct was created because "oops"
was added after "fake_fam" by someone not realizing. Under
__FORTIFY_SOURCE, doing:
memcpy(p->fake_fam, src, len);
raises no warnings when __builtin_object_size(p->fake_fam, 1) returns -1
and may stomp on "oops."
Omitting a warning when using the (invalid) zero-length array is how GCC
treats -fstrict-flex-arrays=3. A warning in that situation is likely an
irritant, because requesting this option level is explicitly requesting
this behavior.
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836
Differential Revision: https://reviews.llvm.org/D134902
157 lines
4.0 KiB
C
157 lines
4.0 KiB
C
// RUN: %clang -target x86_64 -O2 -S -emit-llvm %s -o - 2>&1 | FileCheck --check-prefixes=CHECK,CHECK-NO-STRICT %s
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// RUN: %clang -fstrict-flex-arrays=0 -target x86_64 -O2 -S -emit-llvm %s -o - 2>&1 | FileCheck --check-prefixes=CHECK,CHECK-STRICT-0 %s
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// RUN: %clang -fstrict-flex-arrays=1 -target x86_64 -O2 -S -emit-llvm %s -o - 2>&1 | FileCheck --check-prefixes=CHECK,CHECK-STRICT-1 %s
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// RUN: %clang -fstrict-flex-arrays=2 -target x86_64 -O2 -S -emit-llvm %s -o - 2>&1 | FileCheck --check-prefixes=CHECK,CHECK-STRICT-2 %s
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// RUN: %clang -fstrict-flex-arrays=3 -target x86_64 -O2 -S -emit-llvm %s -o - 2>&1 | FileCheck --check-prefixes=CHECK,CHECK-STRICT-3 %s
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#define OBJECT_SIZE_BUILTIN __builtin_object_size
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typedef struct {
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float f;
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double c[];
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} foo_t;
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typedef struct {
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float f;
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double c[0];
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} foo0_t;
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typedef struct {
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float f;
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double c[1];
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} foo1_t;
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typedef struct {
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float f;
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double c[2];
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} foo2_t;
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// CHECK-LABEL: @bar(
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unsigned bar(foo_t *f) {
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// CHECK-NO-STRICT: ret i32 -1
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// CHECK-STRICT-0: ret i32 -1
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// CHECK-STRICT-1: ret i32 -1
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// CHECK-STRICT-2: ret i32 -1
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// CHECK-STRICT-3: ret i32 -1
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return OBJECT_SIZE_BUILTIN(f->c, 1);
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}
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// CHECK-LABEL: @bar0(
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unsigned bar0(foo0_t *f) {
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// CHECK-NO-STRICT: ret i32 -1
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// CHECK-STRICT-0: ret i32 -1
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// CHECK-STRICT-1: ret i32 -1
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// CHECK-STRICT-2: ret i32 -1
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// CHECK-STRICT-3: ret i32 0
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return OBJECT_SIZE_BUILTIN(f->c, 1);
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}
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// CHECK-LABEL: @bar1(
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unsigned bar1(foo1_t *f) {
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// CHECK-NO-STRICT: ret i32 -1
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// CHECK-STRICT-0: ret i32 -1
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// CHECK-STRICT-1: ret i32 -1
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// CHECK-STRICT-2: ret i32 8
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// CHECK-STRICT-3: ret i32 8
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return OBJECT_SIZE_BUILTIN(f->c, 1);
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}
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// CHECK-LABEL: @bar2(
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unsigned bar2(foo2_t *f) {
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// CHECK-NO-STRICT: ret i32 -1
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// CHECK-STRICT-0: ret i32 -1
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// CHECK-STRICT-1: ret i32 16
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// CHECK-STRICT-2: ret i32 16
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// CHECK-STRICT-3: ret i32 16
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return OBJECT_SIZE_BUILTIN(f->c, 1);
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}
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#define DYNAMIC_OBJECT_SIZE_BUILTIN __builtin_dynamic_object_size
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// CHECK-LABEL: @dyn_bar(
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unsigned dyn_bar(foo_t *f) {
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// CHECK-NO-STRICT: ret i32 -1
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// CHECK-STRICT-0: ret i32 -1
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// CHECK-STRICT-1: ret i32 -1
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// CHECK-STRICT-2: ret i32 -1
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// CHECK-STRICT-3: ret i32 -1
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return DYNAMIC_OBJECT_SIZE_BUILTIN(f->c, 1);
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}
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// CHECK-LABEL: @dyn_bar0(
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unsigned dyn_bar0(foo0_t *f) {
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// CHECK-NO-STRICT: ret i32 -1
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// CHECK-STRICT-0: ret i32 -1
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// CHECK-STRICT-1: ret i32 -1
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// CHECK-STRICT-2: ret i32 -1
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// CHECK-STRICT-3: ret i32 0
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return DYNAMIC_OBJECT_SIZE_BUILTIN(f->c, 1);
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}
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// CHECK-LABEL: @dyn_bar1(
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unsigned dyn_bar1(foo1_t *f) {
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// CHECK-NO-STRICT: ret i32 -1
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// CHECK-STRICT-0: ret i32 -1
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// CHECK-STRICT-1: ret i32 -1
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// CHECK-STRICT-2: ret i32 8
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// CHECK-STRICT-3: ret i32 8
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return DYNAMIC_OBJECT_SIZE_BUILTIN(f->c, 1);
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}
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// CHECK-LABEL: @dyn_bar2(
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unsigned dyn_bar2(foo2_t *f) {
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// CHECK-NO-STRICT: ret i32 -1
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// CHECK-STRICT-0: ret i32 -1
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// CHECK-STRICT-1: ret i32 16
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// CHECK-STRICT-2: ret i32 16
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// CHECK-STRICT-3: ret i32 16
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return DYNAMIC_OBJECT_SIZE_BUILTIN(f->c, 1);
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}
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// Also checks for non-trailing flex-array like members
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typedef struct {
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double c[0];
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float f;
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} foofoo0_t;
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typedef struct {
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double c[1];
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float f;
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} foofoo1_t;
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typedef struct {
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double c[2];
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float f;
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} foofoo2_t;
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// CHECK-LABEL: @babar0(
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unsigned babar0(foofoo0_t *f) {
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// CHECK-NO-STRICT: ret i32 0
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// CHECK-STRICT-0: ret i32 0
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// CHECK-STRICT-1: ret i32 0
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// CHECK-STRICT-2: ret i32 0
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// CHECK-STRICT-3: ret i32 0
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return OBJECT_SIZE_BUILTIN(f->c, 1);
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}
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// CHECK-LABEL: @babar1(
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unsigned babar1(foofoo1_t *f) {
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// CHECK-NO-STRICT: ret i32 8
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// CHECK-STRICT-0: ret i32 8
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// CHECK-STRICT-1: ret i32 8
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// CHECK-STRICT-2: ret i32 8
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// CHECK-STRICT-3: ret i32 8
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return OBJECT_SIZE_BUILTIN(f->c, 1);
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}
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// CHECK-LABEL: @babar2(
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unsigned babar2(foofoo2_t *f) {
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// CHECK-NO-STRICT: ret i32 16
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// CHECK-STRICT-0: ret i32 16
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// CHECK-STRICT-1: ret i32 16
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// CHECK-STRICT-2: ret i32 16
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// CHECK-STRICT-3: ret i32 16
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return OBJECT_SIZE_BUILTIN(f->c, 1);
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}
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