Fix: crystal i REPL fails with pcre2_compile_8 on Windows MinGW

src/compiler/crystal/interpreter/context.cr

@@ -423,10 +423,17 @@ class Crystal::Repl::Context
 
   getter? loader : Loader?
 
+  # Tracks the lib_flags string used at loader initialization. Used to detect
+  # new @[Link] annotations added during incremental REPL evaluation (e.g. the
+  # first use of Regex in the REPL adds pcre2 to lib_flags after the loader
+  # was already initialized with only the prelude's libraries).
+  @loader_lib_flags = ""
+
   getter(loader : Loader) {
     lib_flags = program.lib_flags
     # Execute and expand `subcommands`.
     lib_flags = lib_flags.gsub(/`(.*?)`/) { `#{$1}`.chomp }
+    @loader_lib_flags = lib_flags
 
     args = Process.parse_arguments(lib_flags)
     # FIXME: Part 1: This is a workaround for initial integration of the interpreter:
@@ -477,16 +484,52 @@ class Crystal::Repl::Context
         paths << path
       end
 
+      paths
+    {% elsif flag?(:win32) && flag?(:gnu) %}
+      # MinGW: include the crystal.exe directory (where DLLs live) and PATH
+      paths = [] of String
+
+      if executable_path = Process.executable_path
+        paths << File.dirname(executable_path)
+      end
+
+      ENV["PATH"]?.try &.split(Process::PATH_DELIMITER, remove_empty: true) do |path|
+        paths << path
+      end
+
       paths
     {% else %}
       nil
     {% end %}
   end
 
   def c_function(name : String)
+    # In REPL mode, new @[Link] annotations may be added to lib_flags after the
+    # loader was already initialized (e.g. Regex / pcre2 on first regex use).
+    # Sync the loader with any new libraries before looking up the symbol.
+    if loader?
+      current = program.lib_flags
+      update_loader(current) if current != @loader_lib_flags
+    end
     loader.find_symbol(name)
   end
 
+  # Loads any libraries that appear in *new_lib_flags* but were not present
+  # when the loader was last initialized.
+  private def update_loader(new_lib_flags : String)
+    expanded = new_lib_flags.gsub(/`(.*?)`/) { `#{$1}`.chomp }
+    old_args = Process.parse_arguments(@loader_lib_flags).to_set
+
+    Process.parse_arguments(expanded).each do |arg|
+      next if old_args.includes?(arg)
+      if libname = arg.lchop?("-l")
+        loader.load_library?(libname)
+      end
+    end
+
+    @loader_lib_flags = expanded
+  end
+
   def align(size : Int32) : Int32
     rem = size.remainder(8)
     if rem == 0

src/compiler/crystal/loader/mingw.cr

@@ -19,12 +19,13 @@ require "crystal/system/win32/library_archive"
 class Crystal::Loader
   alias Handle = Void*
 
-  def initialize(@search_paths : Array(String))
+  def initialize(@search_paths : Array(String), @dll_search_paths : Array(String)? = nil)
   end
 
   # Parses linker arguments in the style of `ld`.
   #
-  # This is identical to the Unix loader. *dll_search_paths* has no effect.
+  # This is identical to the Unix loader. *dll_search_paths* is used to locate
+  # DLLs by full path before falling back to bare-name loading.
   def self.parse(args : Array(String), *, search_paths : Array(String) = default_search_paths, dll_search_paths : Array(String)? = nil) : self
     libnames = [] of String
     file_paths = [] of String
@@ -63,7 +64,7 @@ class Crystal::Loader
     libnames << crt_dll
 
     begin
-      loader = new(search_paths)
+      loader = new(search_paths, dll_search_paths)
       loader.load_all(libnames, file_paths)
       loader
     rescue exc : LoadError
@@ -82,6 +83,15 @@ class Crystal::Loader
       address = LibC.GetProcAddress(handle, name.check_no_null_byte)
       return address if address
     end
+
+    if ENV["CRYSTAL_INTERPRETER_LOADER_INFO"]?.presence
+      STDERR.puts "  find_symbol?(#{name}): not found in #{@handles.size} handle(s)"
+      @handles.each_with_index do |h, i|
+        STDERR.puts "    handle[#{i}]=0x#{h.address.to_s(16)} lib=#{@loaded_libraries[i]? || "?"}"
+      end
+    end
+
+    nil
   end
 
   def load_file(path : String | ::Path) : Nil
@@ -101,14 +111,65 @@ class Crystal::Loader
   end
 
   private def load_dll?(dll)
-    handle = open_library(dll)
+    # For DLLs that are already loaded in the process (e.g. libpcre2-8-0.dll
+    # as a load-time dep of crystal.exe), LoadLibraryExW with a bare name can
+    # return a module handle that doesn't work with GetProcAddress.  Try
+    # GetModuleHandleExW first: it returns the canonical HMODULE that the
+    # Windows loader already tracks for the named DLL, and GetProcAddress works
+    # on it reliably.
+    via_get_module = false
+    handle = if LibC.GetModuleHandleExW(0, System.to_wstr(dll), out existing) != 0
+      via_get_module = true
+      existing.as(Handle)
+    else
+      # DLL not yet in process: load by full path when possible to avoid the
+      # same duplicate-handle issue if the DLL appears in the process later.
+      full_path = resolve_dll_full_path(dll)
+      open_library(full_path || dll)
+    end
+
+    if ENV["CRYSTAL_INTERPRETER_LOADER_INFO"]?.presence
+      if handle
+        STDERR.puts "  load_dll?(#{dll}): handle=0x#{handle.address.to_s(16)} via_GetModuleHandleExW=#{via_get_module} path=#{module_filename(handle) || "?"}"
+      else
+        STDERR.puts "  load_dll?(#{dll}): FAILED (handle is null)"
+      end
+    end
+
     return false unless handle
 
     @handles << handle
     @loaded_libraries << (module_filename(handle) || dll)
     true
   end
 
+  # Searches for *dll* by full path in dll_search_paths and in sibling `bin/`
+  # directories relative to each library search path.
+  # Returns the full path if found, or nil to fall back to the bare name.
+  private def resolve_dll_full_path(dll : String) : String?
+    # Skip if it's already a path (contains a separator)
+    return nil if ::Path::SEPARATORS.any? { |sep| dll.includes?(sep) }
+
+    # Search in explicit dll_search_paths first
+    @dll_search_paths.try &.each do |dir|
+      path = File.join(dir, dll)
+      return path if File.file?(path)
+    end
+
+    # Search in library search paths and their sibling bin/ directories.
+    # In a typical MinGW layout, .dll.a files live in lib/ and .dll files in bin/,
+    # so for each search path like D:\Crystal\lib\ we also check D:\Crystal\bin\.
+    @search_paths.each do |lib_dir|
+      bin_dir = File.join(::Path[lib_dir].parent.to_s, "bin")
+      {% for dir in %w(bin_dir lib_dir) %}
+        path = File.join({{dir.id}}, dll)
+        return path if File.file?(path)
+      {% end %}
+    end
+
+    nil
+  end
+
   def load_library(libname : String) : Nil
     load_library?(libname) || raise LoadError.new "cannot find #{Loader.library_filename(libname)}"
   end