Added control messages to warnings

Added the concept of control messages to the warning system, plus the
implementation of the controls "@on"/"@off" to turn warnings on/off.
Moreover, the warning system in the test library adds some other
controls to ease the test of warnings.

testes/all.lua

@@ -209,6 +209,10 @@ if #msgs > 0 then
   warn("#tests not performed:\n  ", m, "\n")
 end
 
+warn("@off")
+warn("******** THIS WARNING SHOULD NOT APPEAR **********")
+warn("******** THIS WARNING ALSO SHOULD NOT APPEAR **********")
+warn("@on")
 print("(there should be two warnings now)")
 warn("#This is ", "an expected", " warning")
 warn("#This is", " another one")

testes/api.lua

@@ -977,6 +977,7 @@ assert(t[7] == nil)
 
 -------------------------------------------------------------------------
 do   -- testing errors during GC
+  warn("@off")
   collectgarbage("stop")
   local a = {}
   for i=1,20 do
@@ -994,6 +995,7 @@ do   -- testing errors during GC
   collectgarbage()
   assert(A == 10)  -- number of normal collections
   collectgarbage("restart")
+  warn("@on")
 end
 -------------------------------------------------------------------------
 -- test for userdata vals

testes/gc.lua

@@ -369,6 +369,7 @@ if T then
     s[n] = i
   end
 
+  warn("@store")
   collectgarbage()
   assert(string.find(_WARN, "error in __gc metamethod"))
   assert(string.match(_WARN, "@(.-)@") == "expected")
@@ -383,6 +384,7 @@ if T then
   for i = 1, 10 do assert(s[i]) end
 
   getmetatable(u).__gc = nil
+  warn("@normal")
 
 end
 print '+'
@@ -475,9 +477,11 @@ end
 
 -- errors during collection
 if T then
+  warn("@store")
   u = setmetatable({}, {__gc = function () error "@expected error" end})
   u = nil
   collectgarbage()
+  warn("@normal")
 end
 
 
@@ -645,7 +649,7 @@ end
 
 -- create several objects to raise errors when collected while closing state
 if T then
-  local error, assert, find = error, assert, string.find
+  local error, assert, find, warn = error, assert, string.find, warn
   local n = 0
   local lastmsg
   local mt = {__gc = function (o)
@@ -659,7 +663,9 @@ if T then
     else
       assert(lastmsg == _WARN)  -- subsequent error messages are equal
     end
+    warn("@store")
     error"@expected warning"
+    warn("@normal")
   end}
   for i = 10, 1, -1 do
     -- create object and preserve it until the end

testes/main.lua

@@ -221,6 +221,28 @@ assert(string.find(getoutput(), "error calling 'print'"))
 RUN('echo "io.stderr:write(1000)\ncont" | lua -e "require\'debug\'.debug()" 2> %s', out)
 checkout("lua_debug> 1000lua_debug> ")
 
+-- test warnings
+RUN('echo "io.stderr:write(1); warn[[XXX]]" | lua -q 2> %s', out)
+checkout("1")
+
+prepfile[[
+warn("@allow")               -- unknown control, ignored
+warn("@off", "XXX", "@off")  -- these are not control messages
+warn("@off")                 -- this one is
+warn("@on", "YYY", "@on")    -- not control, but warn is off
+warn("@off")                 -- keep it off
+warn("@on")                  -- restart warnings
+warn("", "@on")              -- again, no control, real warning
+warn("@on")                  -- keep it "started"
+warn("Z", "Z", "Z")          -- common warning
+]]
+RUN('lua %s 2> %s', prog, out)
+checkout[[
+Lua warning: @offXXX@off
+Lua warning: @on
+Lua warning: ZZZ
+]]
+
 -- test many arguments
 prepfile[[print(({...})[30])]]
 RUN('lua %s %s > %s', prog, string.rep(" a", 30), out)
@@ -355,8 +377,15 @@ if T then   -- test library?
   NoRun("not enough memory", "env MEMLIMIT=100 lua")
 
   -- testing 'warn'
+  warn("@store")
   warn("@123", "456", "789")
   assert(_WARN == "@123456789")
+
+  warn("zip", "", " ", "zap")
+  assert(_WARN == "zip zap")
+  warn("ZIP", "", " ", "ZAP")
+  assert(_WARN == "ZIP ZAP")
+  warn("@normal")
 end
 
 do