Makefiles: Normalize compiler-generated depfile paths

Even though Makefile generators pass source files and include
directories by absolute path to the compiler, the compiler may generate
depfile paths relative to the current working directory.  For example,
`ccache` with `CCACHE_BASEDIR` may transform paths this way.  When
reading a depfile, convert relative dependencies to absolute paths
before placing them in `compiler_depend.make`, which is later evaluated
in the top-level build directory.

Fixes: #22364

1 files changed, 5 insertions, 3 deletions

diff --git a/Source/cmGccDepfileReader.cxx b/Source/cmGccDepfileReader.cxx
index 6436baa..d30dbc3 100644
--- a/Source/cmGccDepfileReader.cxx
+++ b/Source/cmGccDepfileReader.cxx
@@ -12,8 +12,9 @@
 #include "cmStringAlgorithms.h"
 #include "cmSystemTools.h"
 
-cm::optional<cmGccDepfileContent> cmReadGccDepfile(const char* filePath,
-                                                   const std::string& prefix)
+cm::optional<cmGccDepfileContent> cmReadGccDepfile(
+  const char* filePath, const std::string& prefix,
+  GccDepfilePrependPaths prependPaths)
 {
   cmGccDepfileLexerHelper helper;
   if (!helper.readFile(filePath)) {
@@ -23,7 +24,8 @@ cm::optional<cmGccDepfileContent> cmReadGccDepfile(const char* filePath,
 
   for (auto& dep : *deps) {
     for (auto& rule : dep.rules) {
-      if (!prefix.empty() && !cmSystemTools::FileIsFullPath(rule)) {
+      if (prependPaths == GccDepfilePrependPaths::All && !prefix.empty() &&
+          !cmSystemTools::FileIsFullPath(rule)) {
         rule = cmStrCat(prefix, '/', rule);
       }
       if (cmSystemTools::FileIsFullPath(rule)) {