From 6900b21b1180ffa590f3e97d6be75c37707990ca Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Fri, 30 Aug 2024 08:11:26 +0200
Subject: Add absolute compiler path to compiler checksum

In particular, this will allow us to use depdb change tracking to also detect
changes to compilation database entries.
---
 libbuild2/cc/guess.cxx | 10 ++++++----
 libbuild2/cc/guess.hxx |  3 +++
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/libbuild2/cc/guess.cxx b/libbuild2/cc/guess.cxx
index 5ae6fb2..f092933 100644
--- a/libbuild2/cc/guess.cxx
+++ b/libbuild2/cc/guess.cxx
@@ -1878,7 +1878,7 @@ namespace build2
         move (ver),
         nullopt,
         move (gr.signature),
-        "",
+        "",                  // Checksum to be calculated from signature.
         move (t),
         move (ot),
         move (cpat),
@@ -2128,7 +2128,7 @@ namespace build2
         move (ver),
         nullopt,
         move (gr.signature),
-        move (gr.checksum), // Calculated on whole -v output.
+        "",                  // Checksum calculated on whole -v output.
         move (t),
         move (ot),
         move (pat),
@@ -2898,7 +2898,7 @@ namespace build2
         move (ver),
         move (var_ver),
         move (gr.signature),
-        move (gr.checksum), // Calculated on whole -v output.
+        "",                  // Checksum calculated on whole -v output.
         move (t),
         move (ot),
         move (cpat),
@@ -3216,7 +3216,7 @@ namespace build2
         move (ver),
         nullopt,
         move (gr.signature),
-        "",
+        "",                  // Checksum to be calculated from signature.
         move (t),
         move (ot),
         move (pat),
@@ -3370,6 +3370,8 @@ namespace build2
           cs.append (gr.type_signature);
       }
 
+      cs.append (r.path.effect_string ());
+
       r.checksum = cs.string ();
 
       // Derive binutils pattern unless this has already been done by the
diff --git a/libbuild2/cc/guess.hxx b/libbuild2/cc/guess.hxx
index 7cbbd87..dfa8aa2 100644
--- a/libbuild2/cc/guess.hxx
+++ b/libbuild2/cc/guess.hxx
@@ -160,6 +160,9 @@ namespace build2
     // checksum will still change. This is currently the case for all the
     // compilers that we support.
     //
+    // And we assume that the checksum incorporates the absolute compiler
+    // path. This is used to detect compilation database changes.
+    //
     // The target is the compiler's traget architecture triplet. Note that
     // unlike all the preceding fields, this one takes into account the
     // compile options (e.g., -m32).
-- 
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