Merge pull request #18553 from jketema/preprocblock

C++: Update `PreprocBlock.qll` QLDoc and add C++23 test

Author: jketema

cpp/ql/lib/semmle/code/cpp/headers/PreprocBlock.qll

@@ -1,8 +1,9 @@
 /**
  * This library offers a view of preprocessor branches (`#if`, `#ifdef`,
- * `#ifndef`, `#elif` and `#else`) as blocks of code between the opening and
- * closing directives, with navigable parent-child relationships to other
- * blocks. The main class is `PreprocessorBlock`.
+ * `#ifndef`, `#elif`, `#elifdef`, `#elifndef`, and `#else`) as blocks of
+ * code between the opening and closing directives, with navigable
+ * parent-child relationships to other blocks. The main class is
+ * `PreprocessorBlock`.
  */
 
 import cpp
@@ -32,10 +33,10 @@ private int getPreprocIndex(PreprocessorBranchDirective directive) {
 
 /**
  * A chunk of code from one preprocessor branch (`#if`, `#ifdef`,
- * `#ifndef`, `#elif` or `#else`) to the directive that closes it
- * (`#elif`, `#else` or `#endif`).  The `getParent()` method
- * allows these blocks to be navigated as a tree, with the root
- * being the entire file.
+ * `#ifndef`, `#elif`, `#elifdef`, `#elifndef`, or `#else`) to the
+ * directive that closes it (`#elif`, `#elifdef`, `#elifndef`, `#else`,
+ * or `#endif`).  The `getParent()` method allows these blocks to be
+ * navigated as a tree, with the root being the entire file.
  */
 class PreprocessorBlock extends @element {
   PreprocessorBlock() {

cpp/ql/test/library-tests/headers/preprocBlock/preprocblock.expected

@@ -1,10 +1,16 @@
 | #elif defined GREEN | preprocblock.cpp:10:0:11:0 | #ifndef BLUE |
 | #elif defined GREEN | preprocblock.cpp:14:0:15:0 | #if 0 |
 | #elif defined GREEN | preprocblock.cpp:16:0:17:0 | #else |
+| #elifdef GREEN | preprocblock23.cpp:11:0:12:0 | #if 0 |
+| #elifdef GREEN | preprocblock23.cpp:13:0:14:0 | #elifndef BLUE |
 | (no parent) | file://:0:0:0:0 |  |
 | (no parent) | header.h:0:0:8:0 | header.h |
+| (no parent) | preprocblock23.cpp:0:0:22:0 | preprocblock23.cpp |
 | (no parent) | preprocblock.cpp:0:0:25:0 | preprocblock.cpp |
 | header.h | header.h:3:0:7:0 | #ifndef HEADER_H |
+| preprocblock23.cpp | preprocblock23.cpp:7:0:7:0 | #ifdef RED |
+| preprocblock23.cpp | preprocblock23.cpp:8:0:17:0 | #elifdef GREEN |
+| preprocblock23.cpp | preprocblock23.cpp:18:0:21:0 | #else |
 | preprocblock.cpp | preprocblock.cpp:6:0:6:0 | #ifdef RED |
 | preprocblock.cpp | preprocblock.cpp:7:0:20:0 | #elif defined GREEN |
 | preprocblock.cpp | preprocblock.cpp:21:0:24:0 | #else |

cpp/ql/test/library-tests/headers/preprocBlock/preprocblock23.cpp

@@ -0,0 +1,22 @@
+// preprocblock23.cpp
+// semmle-extractor-options: -std=c++23
+
+#include "header.h"
+#define GREEN
+
+#ifdef RED
+#elifdef GREEN
+	#include "header.h"
+
+	#if 0
+		#include "header.h" // not reached
+	#elifndef BLUE
+		#include "header.h"
+	#endif
+
+	#include "header.h"
+#else
+
+	// ...
+
+#endif

cpp/ql/test/library-tests/headers/preprocBlock/preprocinclude.expected

@@ -1,3 +1,7 @@
+| preprocblock23.cpp:4:1:4:19 | #include "header.h" | preprocblock23.cpp:0:0:22:0 | preprocblock23.cpp |
+| preprocblock23.cpp:9:2:9:20 | #include "header.h" | preprocblock23.cpp:8:0:17:0 | #elifdef GREEN |
+| preprocblock23.cpp:14:3:14:21 | #include "header.h" | preprocblock23.cpp:13:0:14:0 | #elifndef BLUE |
+| preprocblock23.cpp:17:2:17:20 | #include "header.h" | preprocblock23.cpp:8:0:17:0 | #elifdef GREEN |
 | preprocblock.cpp:3:1:3:19 | #include "header.h" | preprocblock.cpp:0:0:25:0 | preprocblock.cpp |
 | preprocblock.cpp:8:2:8:20 | #include "header.h" | preprocblock.cpp:7:0:20:0 | #elif defined GREEN |
 | preprocblock.cpp:11:3:11:21 | #include "header.h" | preprocblock.cpp:10:0:11:0 | #ifndef BLUE |