Do not exclude include directory symlinks to entries of CPATH

Extend the fix from commit 2d0b0e2b9d (Do not exclude include
directories made implicit by CPATH, 2019-05-29, v3.14.5~2^2) to cover
include directories that are symlinks to paths listed in `CPATH`.

Compare resolved paths against resolved entries of `CPATH`.
Resolve the entries as late as possible in case symlinks change.

Fixes: #22383

2 files changed, 14 insertions, 4 deletions

diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index 30df4c4..3d36acd 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -109,7 +109,7 @@ cmLocalGenerator::cmLocalGenerator(cmGlobalGenerator* gg, cmMakefile* makefile)
     cmSystemTools::GetPath(cpath, "CPATH");
     for (std::string const& cp : cpath) {
       if (cmSystemTools::FileIsFullPath(cp)) {
-        this->EnvCPATH.emplace(cmSystemTools::CollapseFullPath(cp));
+        this->EnvCPATH.emplace_back(cmSystemTools::CollapseFullPath(cp));
       }
     }
   }
@@ -1248,8 +1248,18 @@ std::vector<BT<std::string>> cmLocalGenerator::GetIncludeDirectoriesImplicit(
 
   bool const isCorCxx = (lang == "C" || lang == "CXX");
 
+  // Resolve symlinks in CPATH for comparison with resolved include paths.
+  // We do this here instead of when EnvCPATH is populated in case symlinks
+  // on disk have changed in the meantime.
+  std::set<std::string> resolvedEnvCPATH;
+  if (isCorCxx) {
+    for (std::string const& i : this->EnvCPATH) {
+      resolvedEnvCPATH.emplace(this->GlobalGenerator->GetRealPath(i));
+    }
+  }
+
   // Checks if this is not an excluded (implicit) include directory.
-  auto notExcluded = [this, &implicitSet, &implicitExclude,
+  auto notExcluded = [this, &implicitSet, &implicitExclude, &resolvedEnvCPATH,
                       isCorCxx](std::string const& dir) -> bool {
     std::string const& real_dir = this->GlobalGenerator->GetRealPath(dir);
     return
@@ -1260,7 +1270,7 @@ std::vector<BT<std::string>> cmLocalGenerator::GetIncludeDirectoriesImplicit(
       // they are implicitly searched by the compiler.  They are meant to be
       // user-specified directories that can be re-ordered or converted to
       // -isystem without breaking real compiler builtin headers.
-      || (isCorCxx && cm::contains(this->EnvCPATH, dir));
+      || (isCorCxx && cm::contains(resolvedEnvCPATH, real_dir));
   };
 
   // Get the target-specific include directories.
diff --git a/Source/cmLocalGenerator.h b/Source/cmLocalGenerator.h
index 993280a..cafb34d 100644
--- a/Source/cmLocalGenerator.h
+++ b/Source/cmLocalGenerator.h
@@ -587,7 +587,7 @@ protected:
   std::string::size_type ObjectPathMax;
   std::set<std::string> ObjectMaxPathViolations;
 
-  std::set<std::string> EnvCPATH;
+  std::vector<std::string> EnvCPATH;
 
   using GeneratorTargetMap =
     std::unordered_map<std::string, cmGeneratorTarget*>;