sanitiseHeaderPathsHook: init

C++ headers often use `__FILE__` in error messages, causing the
development outputs of libraries to leak into the runtime closure
of packages using them. This hook abstracts away a pattern used in
a few places throughout the tree to have headers identify themselves
by a sanitized path that does not cause runtime dependencies.

This does unfortunately mean that compiler error messages will
reference the sanitized path. The only alternatives I can imagine
are to patch compilers to handle `__FILE__` specially, or to have
libraries propagate a hook that removes references. The latter would
potentially need to be propagated recursively due to `#include`
semantics and would be less precise than this.

pkgs/by-name/sa/sanitiseHeaderPathsHook/package.nix

@@ -0,0 +1,18 @@
+{
+  lib,
+  makeSetupHook,
+  removeReferencesTo,
+}:
+
+makeSetupHook {
+  name = "sanitise-header-paths-hook";
+
+  substitutions = {
+    removeReferencesTo = lib.getExe removeReferencesTo;
+  };
+
+  meta = {
+    description = "Setup hook to sanitise header file paths to avoid leaked references through `__FILE__`";
+    maintainers = [ lib.maintainers.emily ];
+  };
+} ./sanitise-header-paths-hook.bash

pkgs/by-name/sa/sanitiseHeaderPathsHook/sanitise-header-paths-hook.bash

@@ -0,0 +1,10 @@
+sanitiseHeaderPaths() {
+  local header
+  while IFS= read -r -d '' header; do
+    nixLog "sanitising header path in $header"
+    sed -i "1i#line 1 \"$header\"" "$header"
+    @removeReferencesTo@ -t "${!outputInclude}" "$header"
+  done < <(find "${!outputInclude}/include" -type f -print0)
+}
+
+preFixupHooks+=(sanitiseHeaderPaths)