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

3 files changed, 17 insertions, 6 deletions

diff --git a/Source/cmDependsCompiler.cxx b/Source/cmDependsCompiler.cxx
index 2b48df9..09f5599 100644
--- a/Source/cmDependsCompiler.cxx
+++ b/Source/cmDependsCompiler.cxx
@@ -131,7 +131,9 @@ bool cmDependsCompiler::CheckDependencies(
             depends.emplace_back(std::move(line));
           }
         } else if (format == "gcc"_s) {
-          auto deps = cmReadGccDepfile(depFile.c_str());
+          auto deps = cmReadGccDepfile(
+            depFile.c_str(), this->LocalGenerator->GetCurrentBinaryDirectory(),
+            GccDepfilePrependPaths::Deps);
           if (!deps) {
             continue;
           }
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)) {
diff --git a/Source/cmGccDepfileReader.h b/Source/cmGccDepfileReader.h
index c8a3748..2433492 100644
--- a/Source/cmGccDepfileReader.h
+++ b/Source/cmGccDepfileReader.h
@@ -8,8 +8,15 @@
 
 #include "cmGccDepfileReaderTypes.h"
 
+enum class GccDepfilePrependPaths
+{
+  All,
+  Deps,
+};
+
 /*
- * Read dependencies file and append prefix to all relative paths
+ * Read dependencies file and prepend prefix to all relative paths
  */
 cm::optional<cmGccDepfileContent> cmReadGccDepfile(
-  const char* filePath, const std::string& prefix = {});
+  const char* filePath, const std::string& prefix = {},
+  GccDepfilePrependPaths prependPaths = GccDepfilePrependPaths::All);