[clang] [clang] use absolute path for builtin headers during module compilation (PR #68023)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-modules

<details>
<summary>Changes</summary>

When including builtin headers as part of a system module, ensure we use absolute paths to those headers. Otherwise the module will fail to compile when specifying relative resource directories.

---
Full diff: https://github.com/llvm/llvm-project/pull/68023.diff


3 Files Affected:

- (modified) clang/lib/Lex/ModuleMap.cpp (+4) 
- (added) clang/test/Modules/Inputs/builtin-headers/module.modulemap (+3) 
- (added) clang/test/Modules/relative-resource-dir.m (+8) 


``````````diff
diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index e8437572ebf4bf6..75dd76a63063274 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -348,6 +348,10 @@ bool ModuleMap::resolveAsBuiltinHeader(
   if (!File)
     return false;
 
+  // Ensure the path to the module directory is absolute, otherwise
+  // builtin headers will fail to resolve when using relative resource
+  // directory paths without a -I.
+  llvm::sys::fs::make_absolute(Path);
   auto Role = headerKindToRole(Header.Kind);
   Module::Header H = {Header.FileName, std::string(Path.str()), *File};
   addHeader(Mod, H, Role);
diff --git a/clang/test/Modules/Inputs/builtin-headers/module.modulemap b/clang/test/Modules/Inputs/builtin-headers/module.modulemap
new file mode 100644
index 000000000000000..78a5b730dc6a925
--- /dev/null
+++ b/clang/test/Modules/Inputs/builtin-headers/module.modulemap
@@ -0,0 +1,3 @@
+module ModuleWithBuiltinHeader [system] {
+    header "float.h"
+}
\ No newline at end of file
diff --git a/clang/test/Modules/relative-resource-dir.m b/clang/test/Modules/relative-resource-dir.m
new file mode 100644
index 000000000000000..1d38fe922e71849
--- /dev/null
+++ b/clang/test/Modules/relative-resource-dir.m
@@ -0,0 +1,8 @@
+// RUN: EXPECTED_RESOURCE_DIR=`%clang -print-resource-dir` && \
+// RUN:  mkdir -p %t && rm -rf %t/resource-dir && \
+// RUN:  cp -R $EXPECTED_RESOURCE_DIR %t/resource-dir
+// RUN: cd %t && %clang -cc1 -x objective-c -fmodules -fmodule-format=obj \
+// RUN:   -fimplicit-module-maps -fmodules-cache-path=%t.mcp \
+// RUN:   -fbuiltin-headers-in-system-modules -resource-dir resource-dir \
+// RUN:   -emit-module %S/Inputs/builtin-headers/module.modulemap \
+// RUN:   -fmodule-name=ModuleWithBuiltinHeader -o %t.pcm

``````````

</details>


https://github.com/llvm/llvm-project/pull/68023