Fix coverage crash when generating a HTML report with missing sources

Author: Jugst3r

testsuite/tests/instr-cov/363-annot-crash/src/pkg.adb

@@ -0,0 +1,6 @@
+package body Pkg is
+   procedure Foo is
+   begin
+      null;
+   end Foo;
+end Pkg;

testsuite/tests/instr-cov/363-annot-crash/src/pkg.ads

@@ -0,0 +1,3 @@
+package Pkg is
+   procedure Foo;
+end Pkg;

testsuite/tests/instr-cov/363-annot-crash/src/test.adb

@@ -0,0 +1,6 @@
+with Pkg;
+
+procedure Test is
+begin
+   Pkg.Foo;
+end Test;

testsuite/tests/instr-cov/363-annot-crash/test.py

@@ -0,0 +1,38 @@
+"""
+Regression test: check that gnatcov does not crash when generating a XML / HTML
+report with missing sources. It used to crash when trying to compute scope
+metrics.
+"""
+
+from e3.fs import mv, sync_tree
+
+import os
+
+from SCOV.minicheck import build_and_run
+from SUITE.cutils import Wdir
+from SUITE.gprutils import GPRswitches
+from SUITE.tutils import gprfor, thistest, xcov
+
+tmp = Wdir("tmp_")
+
+sync_tree(os.path.join("..", "src"), "src")
+
+xcov_args = build_and_run(
+    gprsw=GPRswitches(
+        root_project=gprfor(srcdirs=["src"], mains=["test.adb"])
+    ),
+    covlevel="stmt",
+    mains=["test"],
+    extra_coverage_args=[],
+    trace_mode="src",
+)
+
+# Then hide the sources
+os.mkdir("src_hidden")
+mv(os.path.join("src", "pkg.adb"), "src_hidden")
+
+# Try to generate a HTML, and an XML report
+xcov(xcov_args + ["-axml"], tolerate_messages="warning: can't open")
+xcov(xcov_args + ["-ahtml"], tolerate_messages="warning: can't open")
+
+thistest.result()

tools/gnatcov/annotations.adb

@@ -996,11 +996,24 @@ package body Annotations is
      (FI       : File_Info_Access;
       From, To : Natural) return Li_Stat_Array
    is
-      Result : Li_Stat_Array := (others => 0);
+      Result           : Li_Stat_Array := (others => 0);
+      Actual_To        : Natural := To;
+      Last_Loaded_Line : Natural renames Last_Line (FI);
    begin
-      for L in From .. To loop
+      --  Do not try to retrieve a line that was not loaded (which has an index
+      --  superior to Last_Line (FI)). This can happen when the sources are not
+      --  available. In that case, only loop until the last loaded line is
+      --  reached (it actually corresponds to the last SCO line), and consider
+      --  the subsequent lines as no code.
+
+      if To > Last_Loaded_Line then
+         Result (No_Code) := To - Last_Loaded_Line;
+         Actual_To := Last_Loaded_Line;
+      end if;
+
+      for L in From .. Actual_To loop
          declare
-            LI : constant Line_Info_Access := Get_Line (FI, L);
+            LI : constant Line_Info_Access :=  Get_Line (FI, L);
             S  : constant Any_Line_State := Aggregated_State (LI.all);
          begin
             --  Update counts. Note that No_Code lines are always counted as