// RUN: %clang_analyze_cc1 -analyzer-checker=core.BitwiseShift \
// RUN: -analyzer-config core.BitwiseShift:Pedantic=true \
// RUN: -analyzer-output=text -verify=expected,c \
// RUN: -triple x86_64-pc-linux-gnu -x c %s \
// RUN: -Wno-shift-count-negative -Wno-shift-negative-value \
// RUN: -Wno-shift-count-overflow -Wno-shift-overflow \
// RUN: -Wno-shift-sign-overflow
//
// RUN: %clang_analyze_cc1 -analyzer-checker=core.BitwiseShift \
// RUN: -analyzer-config core.BitwiseShift:Pedantic=true \
// RUN: -analyzer-output=text -verify=expected,cxx \
// RUN: -triple x86_64-pc-linux-gnu -x c++ -std=c++14 %s \
// RUN: -Wno-shift-count-negative -Wno-shift-negative-value \
// RUN: -Wno-shift-count-overflow -Wno-shift-overflow \
// RUN: -Wno-shift-sign-overflow
// This test file verifies the pedantic mode of the BitwiseShift checker, which
// also reports issues that are undefined behavior (according to the standard,
// under C and in C++ before C++20), but would be accepted by many compilers.
// TEST NEGATIVE LEFT OPERAND
//===----------------------------------------------------------------------===//
int negative_left_operand_literal(void) {
return -2 << 2;
// expected-warning@-1 {{Left operand is negative in left shift}}
// expected-note@-2 {{The result of left shift is undefined because the left operand is negative}}
}
int negative_left_operand_symbolic(int left, int right) {
// expected-note@+2 {{Assuming 'left' is < 0}}
// expected-note@+1 {{Taking false branch}}
if (left >= 0)
return 0;
return left >> right;
// expected-warning@-1 {{Left operand is negative in right shift}}
// expected-note@-2 {{The result of right shift is undefined because the left operand is negative}}
}
int negative_left_operand_compound(short arg) {
// expected-note@+2 {{Assuming 'arg' is < 0}}
// expected-note@+1 {{Taking false branch}}
if (arg >= 0)
return 0;
return (arg - 3) << 2;
// expected-warning@-1 {{Left operand is negative in left shift}}
// expected-note@-2 {{The result of left shift is undefined because the left operand is negative}}
}
int double_negative(void) {
// In this case we still report that the right operand is negative, because
// that's the more "serious" issue:
return -2 >> -2;
// expected-warning@-1 {{Right operand is negative in right shift}}
// expected-note@-2 {{The result of right shift is undefined because the right operand is negative}}
}
int single_unknown_negative(int arg) {
// In this case just one of the operands will be negative, so we end up
// reporting the left operand after assuming that the right operand is
// positive.
// expected-note@+2 {{Assuming 'arg' is not equal to 0}}
// expected-note@+1 {{Taking false branch}}
if (!arg)
return 0;
// We're first checking the right operand, record that it must be positive,
// then report that then the left argument must be negative.
return -arg << arg;
// expected-warning@-1 {{Left operand is negative in left shift}}
// expected-note@-2 {{The result of left shift is undefined because the left operand is negative}}
}
void shift_negative_by_zero(int c) {
// This seems to be innocent, but the standard (before C++20) clearly implies
// that this is UB, so we should report it in pedantic mode.
c = (-1) << 0;
// expected-warning@-1 {{Left operand is negative in left shift}}
// expected-note@-2 {{The result of left shift is undefined because the left operand is negative}}
}
// TEST OVERFLOW OF CONCRETE SIGNED LEFT OPERAND
//===----------------------------------------------------------------------===//
// (the most complex and least important part of the checker)
int concrete_overflow_literal(void) {
// 27 in binary is 11011 (5 bits), when shifted by 28 bits it becomes
// 1_10110000_00000000_00000000_00000000
return 27 << 28;
// expected-warning@-1 {{The shift '27 << 28' overflows the capacity of 'int'}}
// cxx-note@-2 {{The shift '27 << 28' is undefined because 'int' can hold only 32 bits (including the sign bit), so 1 bit overflows}}
// c-note@-3 {{The shift '27 << 28' is undefined because 'int' can hold only 31 bits (excluding the sign bit), so 2 bits overflow}}
}
int concrete_overflow_symbolic(int arg) {
// 29 in binary is 11101 (5 bits), when shifted by 29 bits it becomes
// 11_10100000_00000000_00000000_00000000
// expected-note@+2 {{Assuming 'arg' is equal to 29}}
// expected-note@+1 {{Taking false branch}}
if (arg != 29)
return 0;
return arg << arg;
// expected-warning@-1 {{The shift '29 << 29' overflows the capacity of 'int'}}
// cxx-note@-2 {{The shift '29 << 29' is undefined because 'int' can hold only 32 bits (including the sign bit), so 2 bits overflow}}
// c-note@-3 {{The shift '29 << 29' is undefined because 'int' can hold only 31 bits (excluding the sign bit), so 3 bits overflow}}
}
int concrete_overflow_language_difference(void) {
// 21 in binary is 10101 (5 bits), when shifted by 27 bits it becomes
// 10101000_00000000_00000000_00000000
// This does not overflow the 32-bit capacity of int, but reaches the sign
// bit, which is undefined under C (but accepted in C++ even before C++20).
return 21 << 27;
// c-warning@-1 {{The shift '21 << 27' overflows the capacity of 'int'}}
// c-note@-2 {{The shift '21 << 27' is undefined because 'int' can hold only 31 bits (excluding the sign bit), so 1 bit overflows}}
}
int concrete_overflow_int_min(void) {
// Another case that's undefined in C but valid in all C++ versions.
// Note the "represented by 1 bit" special case
return 1 << 31;
// c-warning@-1 {{The shift '1 << 31' overflows the capacity of 'int'}}
// c-note@-2 {{The shift '1 << 31' is undefined because 'int' can hold only 31 bits (excluding the sign bit), so 1 bit overflows}}
}
int concrete_overflow_vague(int arg) {
// expected-note@+2 {{Assuming 'arg' is > 25}}
// expected-note@+1 {{Taking false branch}}
if (arg <= 25)
return 0;
return 1024 << arg;
// expected-warning@-1 {{Left shift of '1024' overflows the capacity of 'int'}}
// cxx-note@-2 {{Left shift of '1024' is undefined because 'int' can hold only 32 bits (including the sign bit), so some bits overflow}}
// c-note@-3 {{Left shift of '1024' is undefined because 'int' can hold only 31 bits (excluding the sign bit), so some bits overflow}}
}
int concrete_overflow_vague_only_c(int arg) {
// A third case that's undefined in C but valid in all C++ versions.
// c-note@+2 {{Assuming 'arg' is > 20}}
// c-note@+1 {{Taking false branch}}
if (arg <= 20)
return 0;
return 1024 << arg;
// c-warning@-1 {{Left shift of '1024' overflows the capacity of 'int'}}
// c-note@-2 {{Left shift of '1024' is undefined because 'int' can hold only 31 bits (excluding the sign bit), so some bits overflow}}
}
int concrete_overflow_vague_left(int arg) {
// This kind of overflow check only handles concrete values on the LHS. With
// some effort it would be possible to report errors in cases like this; but
// it's probably a waste of time especially considering that overflows of
// left shifts became well-defined in C++20.
if (arg <= 1024)
return 0;
return arg << 25; // no-warning
}
int concrete_overflow_shift_zero(void) {
// This is legal, even in C.
// The relevant rule (as paraphrased on cppreference.com) is:
// "For signed LHS with nonnegative values, the value of LHS << RHS is
// LHS * 2^RHS if it is representable in the promoted type of lhs, otherwise
// the behavior is undefined."
return 0 << 31; // no-warning
}
Codebase Browser
llvm