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
60 lines
1.9 KiB
C
60 lines
1.9 KiB
C
// RUN: %clang_cc1 -verify=expected -Warray-bounds-pointer-arithmetic %s
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// RUN: %clang_cc1 -verify=expected -Warray-bounds-pointer-arithmetic %s -fstrict-flex-arrays=0
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// RUN: %clang_cc1 -verify=expected,strict -Warray-bounds-pointer-arithmetic %s -fstrict-flex-arrays=2
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// RUN: %clang_cc1 -verify=expected,strict -Warray-bounds-pointer-arithmetic %s -fstrict-flex-arrays=3
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// Test case from PR10615
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struct ext2_super_block{
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unsigned char s_uuid[8]; // expected-note {{declared here}}
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int ignored; // Prevents "s_uuid" from being treated as a flexible array
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// member.
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};
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void* ext2_statfs (struct ext2_super_block *es,int a) {
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return (void *)es->s_uuid + sizeof(int); // no-warning
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}
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void* broken (struct ext2_super_block *es,int a) {
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return (void *)es->s_uuid + 9; // expected-warning {{the pointer incremented by 9 refers past the end of the array (that has type 'unsigned char[8]')}}
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}
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// Test case reduced from PR11594
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struct S {
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int n;
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};
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void pr11594(struct S *s) {
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int a[10];
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int *p = a - s->n;
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}
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// Test case reduced from <rdar://problem/11387038>. This resulted in
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// an assertion failure because of the typedef instead of an explicit
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// constant array type.
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struct RDar11387038 {};
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typedef struct RDar11387038 RDar11387038Array[1];
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struct RDar11387038_Table {
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RDar11387038Array z; // strict-note {{array 'z' declared here}}
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};
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typedef struct RDar11387038_Table *TPtr;
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typedef TPtr *TabHandle;
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struct RDar11387038_B {
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TabHandle x;
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};
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typedef struct RDar11387038_B RDar11387038_B;
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void radar11387038(void) {
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RDar11387038_B *pRDar11387038_B;
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struct RDar11387038 *y = &(*pRDar11387038_B->x)->z[4]; // strict-warning {{array index 4 is past the end of the array (that has type 'struct RDar11387038[1]')}}
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}
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void pr51682(void) {
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int arr[1];
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switch (0) {
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case 0:
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break;
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case 1:
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asm goto("" ::"r"(arr[42] >> 1)::failed);
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break;
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}
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failed:;
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}
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