From cbb96285de25e950fa9cc63f797cfd08202aea1a Mon Sep 17 00:00:00 2001
From: David McFarland <corngood@gmail.com>
Date: Tue, 21 Oct 2025 14:15:21 -0300
Subject: [PATCH] cygwin-dll-link: allow linkDLLs to be used on individual
 dirs/files

---
 .../cygwin-dll-link-hook/cygwin-dll-link.sh   | 104 +++++++++++++-----
 1 file changed, 75 insertions(+), 29 deletions(-)

diff --git a/pkgs/os-specific/cygwin/cygwin-dll-link-hook/cygwin-dll-link.sh b/pkgs/os-specific/cygwin/cygwin-dll-link-hook/cygwin-dll-link.sh
index 3711ef494ed1..f5d1ae8e0a9c 100644
--- a/pkgs/os-specific/cygwin/cygwin-dll-link-hook/cygwin-dll-link.sh
+++ b/pkgs/os-specific/cygwin/cygwin-dll-link-hook/cygwin-dll-link.sh
@@ -24,39 +24,74 @@ _dllDeps() {
     | sort -u
 }
 
+declare -Ag _linkDeps_visited
+
 _linkDeps() {
-  local target="$1" dir="$2" check="$3"
-  [[ ! -x "$target" ]] && echo "_linkDeps: $target is not executable, skipping." 1>&2 && return
+  local target="$1" dir="$2"
+  if [[ -v _linkDeps_visited[$target] ]]; then
+    echo "_linkDeps: $target was already linked." 1>&2
+    return
+  fi
+  if [[ ! -f "$target" || ! -x "$target" ]]; then
+    echo "_linkDeps: $target is not an executable file, skipping." 1>&2
+    return
+  fi
+
+  local realTarget output inOutput
+  realTarget="$(readlink -f "$target")"
+  for output in $outputs ; do
+    if [[ $realTarget == "${!output}"* ]]; then
+      echo "_linkDeps: $target ($realTarget) is in $output (${!output})." 1>&2
+      inOutput=1
+      break
+    fi
+  done
+
   echo 'target:' "$target"
   local dll
-  _dllDeps "$target" | while read -r dll; do
+  while read -r dll; do
     echo '  dll:' "$dll"
-    if [[ -L "$dir/$dll" || -e "$dir/$dll" ]]; then continue; fi
-    if [[ $dll = cygwin1.dll ]]; then
-      CYGWIN+=\ winsymlinks:nativestrict ln -sr /bin/cygwin1.dll "$dir"
+    if [[ -v _linkDeps_visited[$dir/$dll] ]]; then
+      echo "_linkDeps: $dll was already linked into $dir." 1>&2
       continue
     fi
-    # Locate the DLL - it should be an *executable* file on $HOST_PATH.
-    local dllPath searchPath
-    searchPath=$(dirname "$target"):$_linkDeps_outputPath:$_linkDeps_inputPath:$HOST_PATH
-    if ! dllPath="$(PATH="$searchPath" type -P "$dll")"; then
-      if [[ -z "$check" || -n "${allowedImpureDLLsMap[$dll]}" ]]; then
-        continue
+    if [[ -L "$dir/$dll" || -e "$dir/$dll" ]]; then
+      echo '    already exists'
+      _linkDeps "$dir/$dll" "$dir"
+    else
+      local dllPath
+      if [[ $dll = cygwin1.dll ]]; then
+        dllPath=/bin/cygwin1.dll
+      else
+        local searchPath
+        searchPath=$(dirname "$target"):$_linkDeps_outputPath:$_linkDeps_inputPath:$HOST_PATH
+        # Locate the DLL - it should be an *executable* file on $HOST_PATH.
+        # This intentionally doesn't use $dir because we want to prefer dependencies
+        # that are already linked next to the target.
+        if ! dllPath="$(PATH="$searchPath" type -P "$dll")"; then
+          if [[ -z "$inOutput" || -n "${allowedImpureDLLsMap[$dll]}" ]]; then
+            continue
+          fi
+          echo unable to find "$dll" in "$searchPath" >&2
+          exit 1
+        fi
       fi
-      echo unable to find "$dll" in "$searchPath" >&2
-      exit 1
+      echo '    linking to:' "$dllPath"
+      CYGWIN+=\ winsymlinks:nativestrict ln -sr "$dllPath" "$dir"
+      _linkDeps "$dllPath" "$dir"
     fi
-    echo '    linking to:' "$dllPath"
-    CYGWIN+=\ winsymlinks:nativestrict ln -sr "$dllPath" "$dir"
-    # That DLL might have its own (transitive) dependencies,
-    # so add also all DLLs from its directory to be sure.
-    _linkDeps "$dllPath" "$dir" ""
-  done
+    _linkDeps_visited[$dir/$dll]=1
+  done < <(_dllDeps "$target")
 }
 
+# linkDLLsDir can be used to override the destination path for links.  This is
+# useful if you're trying to link dependencies of libraries into the directory
+# containing an executable.
+#
+# Arguments can be a file or directory path. Directories are searched
+# recursively.
 linkDLLs() {
   # shellcheck disable=SC2154
-  if [ ! -d "$prefix" ]; then return; fi
   (
     set -e
     shopt -s globstar nullglob
@@ -70,15 +105,26 @@ linkDLLs() {
       allowedImpureDLLsMap[$dll]=1
     done
 
-    cd "$prefix"
-
-    # Iterate over any DLL that we depend on.
-    local target
-    for target in {bin,lib,libexec}/**/*.{exe,dll}; do
-      [[ ! -f "$target" || ! -x "$target" ]] ||
-        _linkDeps "$target" "$(dirname "$target")" "1"
+    local target file
+    for target in "$@"; do
+      # Iterate over any DLL that we depend on.
+      if [[ -f "$target" ]]; then
+        _linkDeps "$target" "${linkDLLsDir-$(dirname "$target")}"
+      elif [[ -d "$target" ]]; then
+        for file in "${target%/}"/**/*.{exe,dll}; do
+          _linkDeps "$file" "${linkDLLsDir-$(dirname "$file")}"
+        done
+      else
+        echo "linkDLLs: $target is not a file or directory, skipping." 1>&2
+      fi
     done
   )
 }
 
-fixupOutputHooks+=(linkDLLs)
+_linkDLLs() {
+  # shellcheck disable=SC2154
+  if [[ ! -d $prefix || ${dontLinkDLLs-} ]]; then return; fi
+  linkDLLs "$prefix"/{bin,lib,libexec}/
+}
+
+fixupOutputHooks+=(_linkDLLs)