From c6b484823806e08e1756b1a6066a3ace6f080fae Mon Sep 17 00:00:00 2001
From: Roberto I <roberto@inf.puc-rio.br>
Date: Fri, 30 Jan 2026 16:47:33 -0300
Subject: Environment variable for readline library name

The name of the readline library can be changed from its default value
through environment variable LUA_READLINELIB.
---
 lua.c           | 24 ++++++++++++++++++------
 testes/main.lua | 23 ++++++++++++++++++++++-
 2 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/lua.c b/lua.c
index 37fd1cb8..3f4fc9f7 100644
--- a/lua.c
+++ b/lua.c
@@ -30,6 +30,12 @@
 #define LUA_INIT_VAR		"LUA_INIT"
 #endif
 
+/* Name of the environment variable with the name of the readline library */
+#if !defined(LUA_RLLIB_VAR)
+#define LUA_RLLIB_VAR		"LUA_READLINELIB"
+#endif
+
+
 #define LUA_INITVARVERSION	LUA_INIT_VAR LUA_VERSUFFIX
 
 
@@ -507,18 +513,24 @@ static void lua_freeline (char *line) {
 #include <dlfcn.h>
 
 static void lua_initreadline (lua_State *L) {
-  void *lib = dlopen(LUA_READLINELIB, RTLD_NOW | RTLD_LOCAL);
-  if (lib == NULL)
-    lua_warning(L, "library '" LUA_READLINELIB "' not found", 0);
-  else {
+  const char *rllib = l_getenv(LUA_RLLIB_VAR);  /* name of readline library */
+  void *lib;  /* library handle */
+  if (rllib == NULL)  /* no environment variable? */
+    rllib = LUA_READLINELIB;  /* use default name */
+  lib = dlopen(rllib, RTLD_NOW | RTLD_LOCAL);
+  if (lib != NULL) {
     const char **name = cast(const char**, dlsym(lib, "rl_readline_name"));
     if (name != NULL)
       *name = "lua";
     l_readline = cast(l_readlineT, cast_func(dlsym(lib, "readline")));
     l_addhist = cast(l_addhistT, cast_func(dlsym(lib, "add_history")));
-    if (l_readline == NULL)
-      lua_warning(L, "unable to load 'readline'", 0);
+    if (l_readline != NULL)  /* could load readline function? */
+      return;  /* everything ok */
+    /* else emit a warning */
   }
+  lua_warning(L, "unable to load readline library '", 1);
+  lua_warning(L, rllib, 1);
+  lua_warning(L, "'", 0);
 }
 
 #else		/* }{ */
diff --git a/testes/main.lua b/testes/main.lua
index dc48dc48..98d36951 100644
--- a/testes/main.lua
+++ b/testes/main.lua
@@ -78,6 +78,9 @@ end
 
 RUN('lua -v')
 
+RUN('lua -v > %s', out)
+local release = string.match(getoutput(), "Lua (%d+%.%d+%.%d+)")
+
 print(string.format("(temporary program file used in these tests: %s)", prog))
 
 -- running stdin as a file
@@ -167,7 +170,9 @@ checkout("10\n11\n")
 -- test errors in LUA_INIT
 NoRun('LUA_INIT:1: msg', 'env LUA_INIT="error(\'msg\')" lua')
 
--- test option '-E'
+
+print("testing option '-E'")
+
 local defaultpath, defaultCpath
 
 do
@@ -192,6 +197,22 @@ assert(not string.find(defaultpath, "xxx") and
        string.find(defaultCpath, "lua"))
 
 
+-- (LUA_READLINELIB was introduced in 5.5.1)
+if release >= "5.5.1" then
+  print"testing readline library name"
+  -- should generate a warning when trying to load inexistent library "xuxu"
+  local env = [[LUA_READLINELIB=xuxu LUA_INIT="warn('@allow')"]]
+  local code = 'echo " " | env %s lua %s -W -i >%s 2>&1'
+  RUN(code, env, "", out)   -- run code with no extra options
+  assert(string.find(getoutput(),
+            "warning: unable to load readline library 'xuxu'"))
+
+  RUN(code, env, "-E", out)   -- run again with option -E
+  -- no warning when LUA_READLINELIB is to be ignored
+  assert(not string.find(getoutput(), "warning"))
+end
+
+
 -- test replacement of ';;' to default path
 local function convert (p)
   prepfile("print(package.path)")
-- 
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