commit 8b7cfee26b71e66de2cef9f8db9d9e18f5439afd
parent c1a63c45f8ec5932993c8cec40d3c5ec0743349c
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Wed, 26 Jun 2019 13:26:09 -0300
Small changes around C-stack limit
- Better documentation in 'testes/cstack.lua' about using
'debug.setCstacklimit' to find a good limit.
- Constant LUAI_MAXCSTACK gets added CSTACKERR (extra stack for
error handling), so that it is compatible with the argument to
'debug.setCstacklimit'.
Diffstat:
4 files changed, 24 insertions(+), 10 deletions(-)
diff --git a/lstate.c b/lstate.c
@@ -388,7 +388,7 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
preinit_thread(L, g);
g->allgc = obj2gco(L); /* by now, only object is the main thread */
L->next = NULL;
- g->Cstacklimit = L->nCcalls = LUAI_MAXCSTACK;
+ g->Cstacklimit = L->nCcalls = LUAI_MAXCSTACK + CSTACKERR;
g->frealloc = f;
g->ud = ud;
g->warnf = NULL;
diff --git a/ltests.h b/ltests.h
@@ -31,7 +31,7 @@
/* compiled with -O0, Lua uses a lot of C stack space... */
#undef LUAI_MAXCSTACK
-#define LUAI_MAXCSTACK (400 + CSTACKERR)
+#define LUAI_MAXCSTACK 400
/* to avoid warnings, and to make sure value is really unused */
#define UNUSED(x) (x=0, (void)(x))
diff --git a/luaconf.h b/luaconf.h
@@ -47,7 +47,7 @@
** (It will crash with a limit too high.)
*/
#if !defined(LUAI_MAXCSTACK)
-#define LUAI_MAXCSTACK 2200
+#define LUAI_MAXCSTACK 2000
#endif
diff --git a/testes/cstack.lua b/testes/cstack.lua
@@ -4,15 +4,29 @@
local debug = require "debug"
print"testing C-stack overflow detection"
+print"If this test craches, see its file ('cstack.lua')"
+
+-- Segmentation faults in these tests probably result from a C-stack
+-- overflow. To avoid these errors, you can use the function
+-- 'debug.setCstacklimit' to set a smaller limit for the use of
+-- C stack by Lua. After finding a reliable limit, you might want
+-- to recompile Lua with this limit as the value for
+-- the constant 'LUAI_MAXCCALLS', which defines the default limit.
+-- (The default limit is printed by this test.)
+-- Alternatively, you can ensure a larger stack for the program.
+
+-- For Linux, a limit up to 30_000 seems Ok. Windows cannot go much
+-- higher than 2_000.
+
local origlimit = debug.setCstacklimit(400)
-print("current stack limit: " .. origlimit)
-debug.setCstacklimit(origlimit)
+print("default stack limit: " .. origlimit)
+
+-- change this value for different limits for this test suite
+local currentlimit = origlimit
+debug.setCstacklimit(currentlimit)
+print("current stack limit: " .. currentlimit)
--- Segmentation faults in these tests probably result from a C-stack
--- overflow. To avoid these errors, recompile Lua with a smaller
--- value for the constant 'LUAI_MAXCCALLS' or else ensure a larger
--- stack for the program.
local function checkerror (msg, f, ...)
local s, err = pcall(f, ...)
@@ -104,7 +118,7 @@ do print("testing changes in C-stack limit")
return n
end
- assert(debug.setCstacklimit(400) == origlimit)
+ assert(debug.setCstacklimit(400) == currentlimit)
local lim400 = check()
-- a very low limit (given that the several calls to arive here)
local lowlimit = 38