1.24 release: finalize change notes for C/C++

change-notes/1.24/analysis-cpp.md

@@ -4,6 +4,8 @@ The following changes in version 1.24 affect C/C++ analysis in all applications.
 
 ## General improvements
 
+You can now suppress alerts using either single-line block comments (`/* ... */`) or line comments (`// ...`).
+
 ## New queries
 
 | **Query**                   | **Tags**  | **Purpose**                                                        |
@@ -12,26 +14,29 @@ The following changes in version 1.24 affect C/C++ analysis in all applications.
 
 ## Changes to existing queries
 
+A new taint-tracking library is used by all the security queries that track tainted values
+(`cpp/path-injection`, `cpp/cgi-xss`, `cpp/sql-injection`, `cpp/uncontrolled-process-operation`,
+`cpp/unbounded-write`, `cpp/tainted-format-string`, `cpp/tainted-format-string-through-global`,
+`cpp/uncontrolled-arithmetic`, `cpp/uncontrolled-allocation-size`, `cpp/user-controlled-bypass`,
+`cpp/cleartext-storage-buffer`, `cpp/tainted-permissions-check`).
+These queries now have more precise results and also offer _path explanations_ so you can explore the results easily.
+There is a performance cost to this, and the LGTM query suite will overall run slower than before.
+
 | **Query**                  | **Expected impact**    | **Change**                                                       |
 |----------------------------|------------------------|------------------------------------------------------------------|
+| Boost\_asio TLS Settings Misconfiguration (`cpp/boost/tls-settings-misconfiguration`) | Query id change | The identifier was updated to use dashes in place of underscores (previous identifier `cpp/boost/tls_settings_misconfiguration`). |
 | Buffer not sufficient for string (`cpp/overflow-calculated`) | More true positive results | This query now identifies a wider variety of buffer allocations using the `semmle.code.cpp.models.interfaces.Allocation` library. |
-| No space for zero terminator (`cpp/no-space-for-terminator`) | More true positive results | This query now identifies a wider variety of buffer allocations using the `semmle.code.cpp.models.interfaces.Allocation` library. |
+| Hard-coded Japanese era start date (`cpp/japanese-era/exact-era-date`) |  | This query is no longer run on LGTM. |
 | Memory is never freed (`cpp/memory-never-freed`) | More true positive results | This query now identifies a wider variety of buffer allocations using the `semmle.code.cpp.models.interfaces.Allocation` library. |
 | Memory may not be freed (`cpp/memory-may-not-be-freed`) | More true positive results | This query now identifies a wider variety of buffer allocations using the `semmle.code.cpp.models.interfaces.Allocation` library. |
-| Mismatching new/free or malloc/delete (`cpp/new-free-mismatch`) | Fewer false positive results | Fixed false positive results in template code. |
-| Missing return statement (`cpp/missing-return`) | Fewer false positive results | Functions containing `asm` statements are no longer highlighted by this query. |
-| Missing return statement (`cpp/missing-return`) | More accurate locations | Locations reported by this query are now more accurate in some cases. |
-| No space for zero terminator (`cpp/no-space-for-terminator`) | More correct results | String arguments to formatting functions are now (usually) expected to be null terminated strings. |
-| Hard-coded Japanese era start date (`cpp/japanese-era/exact-era-date`) |  | This query is no longer run on LGTM. |
-| No space for zero terminator (`cpp/no-space-for-terminator`) | Fewer false positive results | This query has been modified to be more conservative when identifying which pointers point to null-terminated strings.  This approach produces fewer, more accurate results. |
+| Mismatching new/free or malloc/delete (`cpp/new-free-mismatch`) | Fewer false positive results | Improved handling of template code gives greater precision. |
+| Missing return statement (`cpp/missing-return`) | Fewer false positive results and more accurate locations | Functions containing `asm` statements are no longer highlighted by this query. The locations reported by this query are now more accurate in some cases. |
+| No space for zero terminator (`cpp/no-space-for-terminator`) | More results with greater precision | The query gives more precise results for a wider variety of buffer allocations. String arguments to formatting functions are now (usually) expected to be null terminated strings. Use of the `semmle.code.cpp.models.interfaces.Allocation` library identifies problems with a wider variety of buffer allocations. This query is also more conservative when identifying which pointers point to null-terminated strings. |
 | Overflow in uncontrolled allocation size (`cpp/uncontrolled-allocation-size`) | Fewer false positive results | The query now produces fewer, more accurate results. Cases where the tainted allocation size is range checked are more reliably excluded. |
 | Overloaded assignment does not return 'this' (`cpp/assignment-does-not-return-this`) | Fewer false positive results | This query no longer reports incorrect results in template classes. |
+| Pointer overflow check (`cpp/pointer-overflow-check`),</br> Possibly wrong buffer size in string copy (`cpp/bad-strncpy-size`),</br> Signed overflow check (`cpp/signed-overflow-check`) | More correct results | A new library is used for determining which expressions have identical value, giving more precise results. There is a performance cost to this, and the LGTM suite will overall run slower than before. |
 | Unsafe array for days of the year (`cpp/leap-year/unsafe-array-for-days-of-the-year`) |  | This query is no longer run on LGTM. |
-| Boost\_asio TLS Settings Misconfiguration (`cpp/boost/tls-settings-misconfiguration`) | Query id change | Query id renamed from `cpp/boost/tls_settings_misconfiguration` (underscores to dashes) |
 | Unsigned comparison to zero (`cpp/unsigned-comparison-zero`) | More correct results | This query now also looks for comparisons of the form `0 <= x`. |
-| Signed overflow check (`cpp/signed-overflow-check`), Pointer overflow check (`cpp/pointer-overflow-check`), Possibly wrong buffer size in string copy (`cpp/bad-strncpy-size`) | More correct results | A new library is used for determining which expressions have identical value, giving more precise results. There is a performance cost to this, and the LGTM suite will overall run slower than before. |
-| All CWE-specific queries using taint tracking (`cpp/path-injection`, `cpp/cgi-xss`, `cpp/sql-injection`, `cpp/uncontrolled-process-operation`, `cpp/unbounded-write`, `cpp/tainted-format-string`, `cpp/tainted-format-string-through-global`, `cpp/uncontrolled-arithmetic`, `cpp/uncontrolled-allocation-size`, `cpp/user-controlled-bypass`, `cpp/cleartext-storage-buffer`, `cpp/tainted-permissions-check`) | More correct results | A new taint-tracking library is used, giving more precise results and offering _path explanations_ for results. There is a performance cost to this, and the LGTM suite will overall run slower than before. |
-
 
 ## Changes to libraries
 
@@ -41,9 +46,9 @@ The following changes in version 1.24 affect C/C++ analysis in all applications.
 * The data-flow library (`semmle.code.cpp.dataflow.DataFlow` and
   `semmle.code.cpp.dataflow.TaintTracking`) has been improved, which affects
   and improves some security queries. The improvements are:
-  - Track flow through functions that combine taint tracking with flow through fields.
-  - Track flow through clone-like functions, that is, functions that read contents of a field from a
-    parameter and stores the value in the field of a returned object.
+    - Track flow through functions that combine taint tracking with flow through fields.
+    - Track flow through clone-like functions, that is, functions that read contents of a field from a
+      parameter and stores the value in the field of a returned object.
 * The security pack taint tracking library
   (`semmle.code.cpp.security.TaintTracking`) uses a new intermediate
   representation. This provides a more precise analysis of flow through
@@ -53,28 +58,27 @@ The following changes in version 1.24 affect C/C++ analysis in all applications.
   (`semmle.code.cpp.valuenumbering.GlobalValueNumbering`) uses a new
   intermediate representation to provide a more precise analysis of
   heap-allocated memory and pointers to stack variables.
-* Created the `semmle.code.cpp.models.interfaces.Allocation` library to model
-  allocation such as `new` expressions and calls to `malloc`. This in intended
-  to replace the functionality in `semmle.code.cpp.commons.Alloc` with a more
-  consistent and useful interface.
-  * The predicate `freeCall` in `semmle.code.cpp.commons.Alloc` has been
-    deprecated. The`Allocation` and `Deallocation` models in
-    `semmle.code.cpp.models.interfaces` should be used instead.
-  * Created the `semmle.code.cpp.models.interfaces.Deallocation` library to
-    model deallocation such as `delete` expressions and calls to `free`. This
-    in intended to replace the functionality in `semmle.code.cpp.commons.Alloc`
-    with a more consistent and useful interface.
+* New libraries have been created to provide a more consistent and useful interface
+  for modeling allocation and deallocation. These replace the old
+  `semmle.code.cpp.commons.Alloc` library.
+    * The new `semmle.code.cpp.models.interfaces.Allocation` library models
+      allocations, such as `new` expressions and calls to `malloc`.
+    * The new `semmle.code.cpp.models.interfaces.Deallocation` library
+      models deallocations, such as `delete` expressions and calls to `free`.
+    * The predicate `freeCall` in `semmle.code.cpp.commons.Alloc` has been
+      deprecated. The `Allocation` and `Deallocation` models in
+      `semmle.code.cpp.models.interfaces` should be used instead.
 * The new class `StackVariable` should be used in place of `LocalScopeVariable`
   in most cases. The difference is that `StackVariable` does not include
   variables declared with `static` or `thread_local`.
-  * As a rule of thumb, custom queries about the _values_ of variables should
-    be changed from `LocalScopeVariable` to `StackVariable`, while queries
-    about the _name or scope_ of variables should remain unchanged.
-  * The `LocalScopeVariableReachability` library is deprecated in favor of
-    `StackVariableReachability`. The functionality is the same.
+    * As a rule of thumb, custom queries about the _values_ of variables should
+      be changed from `LocalScopeVariable` to `StackVariable`, while queries
+      about the _name or scope_ of variables should remain unchanged.
+    * The `LocalScopeVariableReachability` library is deprecated in favor of
+      `StackVariableReachability`. The functionality is the same.
 * Taint tracking and data flow now features better modeling of commonly-used
   library functions:
-  * `gets` and similar functions,
-  * the most common operations on `std::string`,
-  * `strdup` and similar functions, and
-  * formatting functions such as `sprintf`.
+    * `gets` and similar functions,
+    * the most common operations on `std::string`,
+    * `strdup` and similar functions, and
+    * formatting functions such as `sprintf`.