From 072982d83c83b161f555538bad6a82815d1c36eb Mon Sep 17 00:00:00 2001 From: antirez Date: Wed, 4 Jun 2014 18:33:24 +0200 Subject: [PATCH] Scripting: better Lua number -> string conversion in luaRedisGenericCommand(). The lua_to*string() family of functions use a non optimal format specifier when converting integers to strings. This has both the problem of the number being converted in exponential notation, which we don't use as a Redis return value when floating point numbers are involed, and, moreover, there is a loss of precision since the default format specifier is not able to represent numbers that must be represented exactly in the IEEE 754 number mantissa. The new code handles it as a special case using a saner conversion. This fixes issue #1118. --- src/scripting.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/src/scripting.c b/src/scripting.c index 4b485d9b4..2a7f1b910 100644 --- a/src/scripting.c +++ b/src/scripting.c @@ -233,12 +233,22 @@ int luaRedisGenericCommand(lua_State *lua, int raise_error) { char *obj_s; size_t obj_len; - obj_s = (char*)lua_tolstring(lua,j+1,&obj_len); - if (obj_s == NULL) break; /* Not a string. */ + if (lua_isnumber(lua,j+1)) { + /* We can't use lua_tolstring() for number -> string conversion + * since Lua uses a format specifier that loses precision. */ + char dbuf[64]; + lua_Number num = lua_tonumber(lua,j+1); + + obj_len = snprintf(dbuf,sizeof(dbuf),"%.17g",(double)num); + obj_s = dbuf; + } else { + obj_s = (char*)lua_tolstring(lua,j+1,&obj_len); + if (obj_s == NULL) break; /* Not a string. */ + } /* Try to use a cached object. */ - if (j < LUA_CMD_OBJCACHE_SIZE && cached_objects[j] && - cached_objects_len[j] >= obj_len) + if (j < LUA_CMD_OBJCACHE_SIZE && cached_objects[j] && + cached_objects_len[j] >= obj_len) { char *s = cached_objects[j]->ptr; struct sdshdr *sh = (void*)(s-(sizeof(struct sdshdr)));