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__builtin_constant_p(x) is a compiler builtin that evaluates to 1 when its argument x is a compile-time constant and to 0 otherwise. In CodeGen it is simply lowered to the respective LLVM intrinsic. In the Analyzer we've been trying to delegate modeling to Expr::EvaluateAsInt, which is allowed to sometimes fail for no apparent reason. When it fails, let's conservatively return false. Modeling it as false is pretty much never wrong, and it is only required to return true on a best-effort basis, which every user should expect. Fixes VLAChecker false positives on code that tries to emulate static asserts in C by constructing a VLA of dynamic size -1 under the assumption that this dynamic size is actually a constant in the sense of __builtin_constant_p. Differential Revision: https://reviews.llvm.org/D60110 llvm-svn: 357557
85 lines
3.0 KiB
C++
85 lines
3.0 KiB
C++
// RUN: %clang_analyze_cc1 -triple x86_64-apple-darwin10 -analyzer-checker=core,debug.ExprInspection %s -std=c++11 -verify
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void clang_analyzer_eval(bool);
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void clang_analyzer_warnIfReached();
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void testAddressof(int x) {
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clang_analyzer_eval(&x == __builtin_addressof(x)); // expected-warning{{TRUE}}
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}
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void testSize() {
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struct {
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int x;
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int y;
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char z;
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} object;
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clang_analyzer_eval(__builtin_object_size(&object.y, 0) == sizeof(object) - sizeof(int)); // expected-warning{{TRUE}}
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// Clang can't actually evaluate these builtin "calls", but importantly they don't actually evaluate the argument expression either.
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int i = 0;
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char buf[10];
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clang_analyzer_eval(__builtin_object_size(&buf[i++], 0) == sizeof(buf)); // expected-warning{{FALSE}}
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clang_analyzer_eval(__builtin_object_size(&buf[++i], 0) == sizeof(buf) - 1); // expected-warning{{FALSE}}
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clang_analyzer_eval(i == 0); // expected-warning{{TRUE}}
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}
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void test_assume_aligned_1(char *p) {
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char *q;
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q = (char*) __builtin_assume_aligned(p, 16);
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clang_analyzer_eval(p == q); // expected-warning{{TRUE}}
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}
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void test_assume_aligned_2(char *p) {
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char *q;
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q = (char*) __builtin_assume_aligned(p, 16, 8);
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clang_analyzer_eval(p == q); // expected-warning{{TRUE}}
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}
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void test_assume_aligned_3(char *p) {
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void *q;
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q = __builtin_assume_aligned(p, 16, 8);
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clang_analyzer_eval(p == q); // expected-warning{{TRUE}}
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}
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void test_assume_aligned_4(char *p) {
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char *q;
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q = (char*) __builtin_assume_aligned(p + 1, 16);
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clang_analyzer_eval(p == q); // expected-warning{{FALSE}}
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}
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void f(int i) {
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__builtin_assume(i < 10);
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clang_analyzer_eval(i < 15); // expected-warning {{TRUE}}
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}
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void g(int i) {
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if (i > 5) {
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__builtin_assume(i < 5);
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clang_analyzer_warnIfReached(); // Assumtion contradicts constraints.
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// We give up the analysis on this path.
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}
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}
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void test_constant_p(void *ptr) {
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int i = 1;
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const int j = 2;
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constexpr int k = 3;
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clang_analyzer_eval(__builtin_constant_p(42) == 1); // expected-warning {{TRUE}}
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clang_analyzer_eval(__builtin_constant_p(i) == 0); // expected-warning {{TRUE}}
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clang_analyzer_eval(__builtin_constant_p(j) == 1); // expected-warning {{TRUE}}
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clang_analyzer_eval(__builtin_constant_p(k) == 1); // expected-warning {{TRUE}}
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clang_analyzer_eval(__builtin_constant_p(i + 42) == 0); // expected-warning {{TRUE}}
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clang_analyzer_eval(__builtin_constant_p(j + 42) == 1); // expected-warning {{TRUE}}
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clang_analyzer_eval(__builtin_constant_p(k + 42) == 1); // expected-warning {{TRUE}}
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clang_analyzer_eval(__builtin_constant_p(" ") == 1); // expected-warning {{TRUE}}
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clang_analyzer_eval(__builtin_constant_p(test_constant_p) == 0); // expected-warning {{TRUE}}
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clang_analyzer_eval(__builtin_constant_p(k - 3) == 0); // expected-warning {{FALSE}}
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clang_analyzer_eval(__builtin_constant_p(k - 3) == 1); // expected-warning {{TRUE}}
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clang_analyzer_eval(__builtin_constant_p(ptr == 0)); // expected-warning {{FALSE}}
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}
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