[NFC][analyzer] OOB test consolidation IV: rename files (#129697)

This commit finishes the reorganization of the tests for the checker
`security.ArrayBound`.

Previously these tests were all named `out-of-bounds-*` which was only
weakly connected to the checker name; this commit moves them to a
directory named after the checker (`ArrayBound`). I decided to use a
directory instead of the more common filename prefix ("poor man's
directory") system because it seems to be a more natural use of the
filesystem and there are already a few precedents for it.

I also added (or edited) comments at the beginning of each test file to
describe their purpose; and I added a single new testcase to highlight
that the assumption note tags can be added to reports by any checker.
(Previously all tests in the file triggered out-of-bounds reports to
reveal the note tags; but that was just for convenience.)

clang/test/Analysis/ArrayBound/assumption-reporting.c

@@ -1,6 +1,16 @@
 // RUN: %clang_analyze_cc1 -Wno-array-bounds -analyzer-output=text        \
 // RUN:     -analyzer-checker=core,security.ArrayBound,unix.Malloc,optin.taint -verify %s
 
+// When the checker security.ArrayBound encounters an array subscript operation
+// that _may be_ in bounds, it assumes that indexing _is_ in bound. These
+// assumptions will be reported to the user if the execution path leads to a
+// bug report (made by any checker) and the symbol which was constrainted by
+// the assumption is marked as interesting (with `markInteresting` or
+// indirectly via `trackExpressionValue`) in that bug report.
+//
+// This test file validates the content of these note tags which describe the
+// assumptions for the user.
+
 int TenElements[10];
 
 int irrelevantAssumptions(int arg) {
@@ -197,3 +207,14 @@ int *extentInterestingness(int arg) {
   // expected-warning@-1 {{Out of bound access to memory after the end of the heap area}}
   // expected-note@-2 {{Access of 'int' element in the heap area at index 12}}
 }
+
+int triggeredByAnyReport(int arg) {
+  // Verify that note tags explaining the assumptions made by ArrayBound are
+  // not limited to ArrayBound reports but will appear on any bug report (that
+  // marks the relevant symbol as interesting).
+  TenElements[arg + 10] = 8;
+  // expected-note@-1 {{Assuming index is non-negative and less than 10, the number of 'int' elements in 'TenElements'}}
+  return 1024 >> arg;
+  // 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}}
+}

clang/test/Analysis/ArrayBound/brief-tests.c

@@ -1,5 +1,10 @@
 // RUN: %clang_analyze_cc1 -Wno-array-bounds -analyzer-checker=core,security.ArrayBound,debug.ExprInspection -verify %s
 
+// Miscellaneous tests for `security.ArrayBound` where we only test the
+// presence or absence of a bug report. If a test doesn't fit in a more
+// specific file and doesn't need to verify the details of 'note' diagnostics,
+// then it should be placed here.
+
 void clang_analyzer_value(int);
 
 // Tests doing an out-of-bounds access after the end of an array using:

clang/test/Analysis/ArrayBound/cplusplus.cpp

@@ -1,5 +1,7 @@
 // RUN: %clang_analyze_cc1 -std=c++11 -Wno-array-bounds -analyzer-checker=unix,core,security.ArrayBound -verify %s
 
+// Test the interactions of `security.ArrayBound` with C++ features.
+
 // Tests doing an out-of-bounds access after the end of an array using:
 // - constant integer index
 // - constant integer size for buffer
@@ -150,15 +152,13 @@ void test_dynamic_size(int s) {
 }
 //Tests complex arithmetic
 //in new expression
-void test_dynamic_size2(unsigned m,unsigned n){
+void test_dynamic_size2(unsigned m, unsigned n){
   unsigned *U = nullptr;
   U = new unsigned[m + n + 1];
 }
 
 //Test creating invalid references, which break the invariant that a reference
 //is always holding a value, and could lead to nasty runtime errors.
-//(This is not related to operator new, but placed in this file because the
-//other test files are not C++.)
 int array[10] = {0};
 
 void test_after_the_end_reference() {
@@ -179,4 +179,3 @@ int test_reference_that_might_be_after_the_end(int idx) {
     return -1;
   return ref;
 }
-

clang/test/Analysis/ArrayBound/verbose-tests.c

@@ -1,6 +1,11 @@
 // RUN: %clang_analyze_cc1 -Wno-array-bounds -analyzer-output=text        \
 // RUN:     -analyzer-checker=core,security.ArrayBound,unix.Malloc,optin.taint -verify %s
 
+// Miscellaneous tests for `security.ArrayBound` where we also verify the
+// content of the 'note' diagnostics. This makes the tests sensitive to textual
+// changes in the diagnostics, so prefer adding new tests to `brief-tests.c`
+// unless they need to verify the correctness of 'note' diagnostics.
+
 int TenElements[10];
 
 void arrayUnderflow(void) {