C++: Add a new 'Location.isBefore' predicate that also considers columns.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/Location.qll

@@ -73,8 +73,24 @@ class Location extends @location {
 
   /** Holds if `this` comes on a line strictly before `l`. */
   pragma[inline]
-  predicate isBefore(Location l) {
-    this.getFile() = l.getFile() and this.getEndLine() < l.getStartLine()
+  predicate isBefore(Location l) { isBefore(l, false) }
+
+  /**
+   * Holds if `this` comes strictly before `l`. The boolean `sameLine` is
+   * true if `l` is on the same line as `this`, but starts at a later column.
+   * Otherwise, `sameLine` is false.
+   */
+  pragma[inline]
+  predicate isBefore(Location l, boolean sameLine) {
+    this.getFile() = l.getFile() and
+    (
+      sameLine = false and
+      this.getEndLine() < l.getStartLine()
+      or
+      sameLine = true and
+      this.getEndLine() = l.getStartLine() and
+      this.getEndColumn() < l.getStartColumn()
+    )
   }
 
   /** Holds if location `l` is completely contained within this one. */

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/IRConstruction.qll

@@ -349,7 +349,7 @@ Instruction getInstructionBackEdgeSuccessor(Instruction instruction, EdgeKind ki
 
 /** Holds if `goto` jumps strictly forward in the program text. */
 private predicate isStrictlyForwardGoto(GotoStmt goto) {
-  goto.getLocation().isBefore(goto.getTarget().getLocation())
+  goto.getLocation().isBefore(goto.getTarget().getLocation(), _)
 }
 
 Locatable getInstructionAst(TStageInstruction instr) {

cpp/ql/test/library-tests/ir/ir/raw_ir.expected

@@ -8844,16 +8844,13 @@ ir.cpp:
 
 # 1693| int goto_on_same_line()
 # 1693|   Block 0
-# 1693|     v1693_1(void)       = EnterFunction      : 
-# 1693|     mu1693_2(unknown)   = AliasedDefinition  : 
-# 1693|     mu1693_3(unknown)   = InitializeNonLocal : 
-# 1694|     r1694_1(glval<int>) = VariableAddress[x] : 
-# 1694|     r1694_2(int)        = Constant[42]       : 
-# 1694|     mu1694_3(int)       = Store[x]           : &:r1694_1, r1694_2
-# 1695|     v1695_1(void)       = NoOp               : 
-#-----|   Goto (back edge) -> Block 1
-
-# 1695|   Block 1
+# 1693|     v1693_1(void)       = EnterFunction            : 
+# 1693|     mu1693_2(unknown)   = AliasedDefinition        : 
+# 1693|     mu1693_3(unknown)   = InitializeNonLocal       : 
+# 1694|     r1694_1(glval<int>) = VariableAddress[x]       : 
+# 1694|     r1694_2(int)        = Constant[42]             : 
+# 1694|     mu1694_3(int)       = Store[x]                 : &:r1694_1, r1694_2
+# 1695|     v1695_1(void)       = NoOp                     : 
 # 1695|     v1695_2(void)       = NoOp                     : 
 # 1696|     r1696_1(glval<int>) = VariableAddress[#return] : 
 # 1696|     r1696_2(glval<int>) = VariableAddress[x]       :