diff --git a/src/compile/c_gen.cpp b/src/compile/c_gen.cpp
index 56fe719..3df1480 100644
--- a/src/compile/c_gen.cpp
+++ b/src/compile/c_gen.cpp
@@ -3073,8 +3073,7 @@ std::string CGen::CompileNumericExp(const SyntaxTreeInterfacePtr &exp) {
             if (ConstNumberExpIsIntValue(kind, exp)) {
                 return std::to_string(int_value);
             }
-            const double d = (kind == TableKeyKind::kInt) ? static_cast<double>(int_value) : float_value;
-            return FormatCDoubleLiteral(d);
+            return FormatCDoubleLiteral(ConstNumberExpToDouble(kind, int_value, float_value, exp));
         }
     }
 
diff --git a/src/compile/c_runtime_header.h b/src/compile/c_runtime_header.h
index d263477..a4ea669 100644
--- a/src/compile/c_runtime_header.h
+++ b/src/compile/c_runtime_header.h
@@ -1257,7 +1257,23 @@ static inline int FlVarToStr(CVar v, char *buf, int buf_size) {
         case VAR_NIL: memcpy(buf, "nil", 3); buf[3] = '\0'; return 3;
         case VAR_BOOL: if (v.data_.b) { memcpy(buf, "true", 4); buf[4] = '\0'; return 4; } else { memcpy(buf, "false", 5); buf[5] = '\0'; return 5; }
         case VAR_INT: return snprintf(buf, buf_size, "%lld", (long long)v.data_.i);
-        case VAR_FLOAT: return snprintf(buf, buf_size, "%.17g", v.data_.f);
+        case VAR_FLOAT: {
+            /* Lua 5.4 tostringbuff: %.14g，结果只含数字和符号时补 .0 */
+            int flen = snprintf(buf, buf_size, "%.14g", v.data_.f);
+            int fi = 0;
+            if (flen > 0 && flen < buf_size) {
+                if (buf[fi] == '-') fi++;
+                for (; fi < flen; fi++) {
+                    if (buf[fi] < '0' || buf[fi] > '9') break;
+                }
+                if (fi == flen && flen + 2 < buf_size) {
+                    buf[flen] = '.';
+                    buf[flen + 1] = '0';
+                    flen += 2;
+                }
+            }
+            return flen;
+        }
         case VAR_STRING:
         case VAR_STRINGID: FakeluaThrowError(_S, "FlVarToStr: string type should be handled by caller"); return 0;
         case VAR_TABLE: { int __n = snprintf(buf, buf_size - 1, "table(0x%llx", (unsigned long long)(uintptr_t)v.data_.t); if (__n > 0 && __n < buf_size - 1) { buf[__n] = ')'; buf[__n + 1] = '\0'; return __n + 1; } return __n; }
diff --git a/src/compile/compile_common.h b/src/compile/compile_common.h
index cf21dcb..ee26209 100644
--- a/src/compile/compile_common.h
+++ b/src/compile/compile_common.h
@@ -427,6 +427,31 @@ inline bool ConstNumberExpIsIntValue(TableKeyKind kind, const SyntaxTreeInterfac
     return kind == TableKeyKind::kInt && !ConstNumberExpHasFloatSyntax(node);
 }
 
+// 值语境（区别于表键归一化）下，把 ClassifyConstNumberExp 的结果还原成 double。
+// 0.0 会被表键归一化成 int 零，但 Lua 值语义里 0.0 是 float；一元负号作用于
+// 浮点零还必须保留负零：奇数次负号 -> -0.0，偶数次 -> +0.0。
+inline double ConstNumberExpToDouble(TableKeyKind kind, int64_t int_value, double float_value, const SyntaxTreeInterfacePtr &node) {
+    double d = (kind == TableKeyKind::kInt) ? static_cast<double>(int_value) : float_value;
+    if (d == 0.0 && ConstNumberExpHasFloatSyntax(node)) {
+        int minuses = 0;
+        SyntaxTreeInterfacePtr cur = node;
+        for (;;) {
+            const auto un = std::dynamic_pointer_cast<SyntaxTreeExp>(cur);
+            if (!un || un->GetExpKind() != ExpKind::kUnop) {
+                break;
+            }
+            const auto op = std::dynamic_pointer_cast<SyntaxTreeUnop>(un->Op());
+            if (!op || op->GetOpKind() != UnOpKind::kMinus) {
+                break;
+            }
+            ++minuses;
+            cur = un->Right();
+        }
+        d = (minuses % 2 != 0) ? -0.0 : 0.0;
+    }
+    return d;
+}
+
 inline std::string FormatCDoubleLiteral(double d) {
     std::string s = std::format("{:.17g}", d);
     if (s.find('.') == std::string::npos && s.find('e') == std::string::npos && s.find('E') == std::string::npos) {
diff --git a/src/interp/codegen.cpp b/src/interp/codegen.cpp
index 9e5356a..00cae67 100644
--- a/src/interp/codegen.cpp
+++ b/src/interp/codegen.cpp
@@ -218,8 +218,7 @@ CVar InterpCodegen::LiteralFromExp(const SyntaxTreeInterfacePtr &exp) {
                 if (ConstNumberExpIsIntValue(kind, exp)) {
                     return interp_rt::Int(int_value);
                 }
-                const double d = (kind == TableKeyKind::kInt) ? static_cast<double>(int_value) : float_value;
-                return interp_rt::Float(d);
+                return interp_rt::Float(ConstNumberExpToDouble(kind, int_value, float_value, exp));
             }
             return interp_rt::Nil();
         }
@@ -1332,8 +1331,7 @@ int InterpCodegen::CompileExp(const SyntaxTreeInterfacePtr &exp, bool preserve_m
             if (ConstNumberExpIsIntValue(kind, exp)) {
                 LoadConstTo(r, interp_rt::Int(int_value));
             } else {
-                const double d = (kind == TableKeyKind::kInt) ? static_cast<double>(int_value) : float_value;
-                LoadConstTo(r, interp_rt::Float(d));
+                LoadConstTo(r, interp_rt::Float(ConstNumberExpToDouble(kind, int_value, float_value, exp)));
             }
             return r;
         }
diff --git a/src/interp/runtime.cpp b/src/interp/runtime.cpp
index 10b3de9..e149399 100644
--- a/src/interp/runtime.cpp
+++ b/src/interp/runtime.cpp
@@ -4,6 +4,7 @@
 #include "state/const_string.h"
 #include "state/state.h"
 #include "util/exception.h"
+#include "util/number_util.h"
 #include "var/var.h"
 #include "var/var_closure.h"
 #include "var/var_multi.h"
@@ -42,9 +43,7 @@ CVar BinConcat(State *s, const CVar &a, const CVar &b) {
         }
         if (v.type_ == kInt) buf = std::to_string(v.data_.i);
         else {
-            char tmp[256];
-            std::snprintf(tmp, sizeof(tmp), "%.17g", v.data_.f);
-            buf = tmp;
+            buf = FormatLuaFloat(v.data_.f);
         }
         p = buf.c_str();
         len = static_cast<int>(buf.size());
diff --git a/src/native/basic/native_basic.cpp b/src/native/basic/native_basic.cpp
index 277b59f..d0ff511 100644
--- a/src/native/basic/native_basic.cpp
+++ b/src/native/basic/native_basic.cpp
@@ -197,7 +197,8 @@ void RegisterBasicLibraryApi(State *s) {
         for (int i = 0; i < n; ++i) {
             if (i > 0) std::printf("\t");
             CVar arg = inter::GetNativeArg(state, args, n, i);
-            std::string str = AsVar(arg).ToString();
+            // Lua 的 print 对每个参数走 tostring，字符串不带引号
+            std::string str = AsVar(arg).ToString(/*has_quote=*/false, /*has_postfix=*/false);
             std::printf("%s", str.c_str());
         }
         std::printf("\n");
diff --git a/src/native/log/native_log.cpp b/src/native/log/native_log.cpp
index 7cd2012..71f5897 100644
--- a/src/native/log/native_log.cpp
+++ b/src/native/log/native_log.cpp
@@ -1,6 +1,7 @@
 #include "native/log/native_log.h"
 #include "native/native_common.h"
 #include "util/logging.h"
+#include "util/number_util.h"
 
 #include <string>
 #include <string_view>
@@ -27,12 +28,9 @@ static std::string FormatArgs(State *s, CVar *args, int n) {
             case static_cast<int>(VarType::Int):
                 result += std::to_string(arg.data_.i);
                 break;
-            case static_cast<int>(VarType::Float): {
-                char buf[64];
-                std::snprintf(buf, sizeof(buf), "%.17g", arg.data_.f);
-                result += buf;
+            case static_cast<int>(VarType::Float):
+                result += FormatLuaFloat(arg.data_.f);
                 break;
-            }
             case static_cast<int>(VarType::String):
             case static_cast<int>(VarType::StringId):
                 result += inter::FakeluaToNativeString(s, arg);
diff --git a/src/native/string/native_string.cpp b/src/native/string/native_string.cpp
index 80400e6..783bdd4 100644
--- a/src/native/string/native_string.cpp
+++ b/src/native/string/native_string.cpp
@@ -1144,17 +1144,14 @@ void RegisterStringLibraryApi(State *s) {
                 }
                 res.push_back('"');
             } else if (spec == 's') {
-                // 标准 Lua：%s 的参数必须是 string/number，Bool/Table 不合法
-                if (curr_arg.type_ == static_cast<int>(VarType::Bool) || curr_arg.type_ == static_cast<int>(VarType::Table)) {
+                // Lua 5.4：%s 等价于对参数调 tostring（luaL_tolstring）：
+                // string/number/bool/nil 都合法；table 没有 __tostring 元方法才报错
+                if (curr_arg.type_ == static_cast<int>(VarType::Table)) {
                     ThrowFakeluaException("bad argument to 'format' (string expected)");
                 }
                 std::string sval;
                 if (curr_arg.type_ == static_cast<int>(VarType::String) || curr_arg.type_ == static_cast<int>(VarType::StringId)) {
                     sval = std::string(KeyToStringView(curr_arg));
-                } else if (curr_arg.type_ == static_cast<int>(VarType::Int)) {
-                    sval = std::to_string(curr_arg.data_.i);
-                } else if (curr_arg.type_ == static_cast<int>(VarType::Float)) {
-                    sval = std::to_string(curr_arg.data_.f);
                 } else {
                     sval = AsVar(curr_arg).ToString(/*has_quote=*/false, /*has_postfix=*/false);
                 }
@@ -1403,13 +1400,17 @@ void RegisterStringLibraryApi(State *s) {
         std::string_view pat_view = GetStringArgView(a1, temp1);
         const size_t slen = sv.size();
 
-        int64_t max_replace = -1;
+        // Lua 5.4：第四参缺省/nil 时默认 srcl+1（即不限次数）；显式传入的值
+        // 原样使用，负数或 0 意味着一次都不替换（while (n < max_s)）。
+        int64_t max_replace = static_cast<int64_t>(slen) + 1;
         if (n >= 4) {
             CVar a3 = inter::GetNativeArg(state, args, n, 3);
-            if (a3.type_ == static_cast<int>(VarType::Bool) || a3.type_ == static_cast<int>(VarType::Table)) {
-                ThrowFakeluaException("bad argument #4 to 'string.gsub' (number expected)");
+            if (a3.type_ != static_cast<int>(VarType::Nil)) {
+                if (a3.type_ == static_cast<int>(VarType::Bool) || a3.type_ == static_cast<int>(VarType::Table)) {
+                    ThrowFakeluaException("bad argument #4 to 'string.gsub' (number expected)");
+                }
+                max_replace = inter::CVarToInteger(a3, max_replace);
             }
-            max_replace = inter::CVarToInteger(a3, -1);
         }
 
         // 标准 Lua：gsub 的替换参数必须是 string/function/table，Bool 不合法
@@ -1431,7 +1432,7 @@ void RegisterStringLibraryApi(State *s) {
         size_t prev_end = std::numeric_limits<size_t>::max();// 上一次产出匹配的尾后位置
         int64_t count = 0;
 
-        while ((max_replace < 0 || count < max_replace) && src <= slen) {
+        while (count < max_replace && src <= slen) {
             // 从 src 起逐位尝试；与 gmatch 相同的零宽规则：起点处的零宽匹配若紧跟上
             // 一次产出匹配的尾后位置，则跳过该位继续找（避免相邻空匹配）。
             lua_pattern::MatchResult m;
diff --git a/src/native/table/native_table.cpp b/src/native/table/native_table.cpp
index d9caccc..775ba80 100644
--- a/src/native/table/native_table.cpp
+++ b/src/native/table/native_table.cpp
@@ -5,6 +5,7 @@
 #include "native/string/native_string.h"
 #include "state/state.h"
 #include "util/exception.h"
+#include "util/number_util.h"
 #include "var/var.h"
 #include "var/var_closure.h"
 #include "var/var_string.h"
@@ -821,7 +822,7 @@ void RegisterTableLibraryApi(State *s) {
                 parts.push_back(owned.back());
                 total += owned.back().size();
             } else if (item.type_ == static_cast<int>(VarType::Float)) {
-                owned.push_back(std::format("{}", item.data_.f));
+                owned.push_back(FormatLuaFloat(item.data_.f));
                 parts.push_back(owned.back());
                 total += owned.back().size();
             } else if (item.type_ == static_cast<int>(VarType::String) || item.type_ == static_cast<int>(VarType::StringId)) {
diff --git a/src/util/number_util.h b/src/util/number_util.h
index c05c216..65d0a24 100644
--- a/src/util/number_util.h
+++ b/src/util/number_util.h
@@ -1,11 +1,41 @@
 #pragma once
 
 #include <cmath>
+#include <cstdio>
+#include <cstring>
 #include <limits>
 #include <optional>
+#include <string>
 
 namespace fakelua {
 
+// Lua 5.4 number-to-string rule (lobject.c::tostringbuff):
+// format with "%.14g"; if the result looks like an integer (only sign and
+// digits), append ".0" so that floats never print in integer shape.
+// Keeps float/integer distinguishable across tostring -> tonumber round-trips.
+inline std::string FormatLuaFloat(double value) {
+    char buf[64];
+    int len = std::snprintf(buf, sizeof(buf), "%.14g", value);
+    if (len <= 0) {
+        return {};
+    }
+    // Equivalent to Lua's buff[strspn(buff, "-0123456789")] == '\0'
+    size_t i = 0;
+    if (buf[i] == '-') {
+        ++i;
+    }
+    for (; i < static_cast<size_t>(len); ++i) {
+        if (buf[i] < '0' || buf[i] > '9') {
+            break;
+        }
+    }
+    if (i == static_cast<size_t>(len) && static_cast<size_t>(len) + 2 < sizeof(buf)) {
+        buf[len++] = '.';
+        buf[len++] = '0';
+    }
+    return std::string(buf, static_cast<size_t>(len));
+}
+
 // Try to convert a double to int64_t if it's a finite integer value within int64_t range.
 // Returns nullopt if the conversion is not possible.
 // The upper bound must be checked as "< 2^63" rather than "<= INT64_MAX" because
diff --git a/src/var/var.cpp b/src/var/var.cpp
index 8d609a6..147fca8 100644
--- a/src/var/var.cpp
+++ b/src/var/var.cpp
@@ -3,6 +3,7 @@
 #include "state/const_string.h"
 #include "state/state.h"
 #include "util/common.h"
+#include "util/number_util.h"
 #include "var_multi.h"
 #include "var_string.h"
 
@@ -56,7 +57,7 @@ std::string Var::ToString(bool has_quote, bool has_postfix) const {
             ret = std::to_string(data_.i);
             break;
         case VarType::Float: {
-            ret = std::format("{}", data_.f);
+            ret = FormatLuaFloat(data_.f);
             break;
         }
         case VarType::String:
diff --git a/test/lua/basic/test_basic_tostring_cases.lua b/test/lua/basic/test_basic_tostring_cases.lua
index 87babcf..2bcc0ce 100644
--- a/test/lua/basic/test_basic_tostring_cases.lua
+++ b/test/lua/basic/test_basic_tostring_cases.lua
@@ -83,5 +83,28 @@ function test_basic_tostring_edge()
     local round4 = tonumber(tostring(orig4))
     if round4 ~= orig4 then return 54 end
 
+    -- -------------------------------------------------------------------------
+    -- Lua 5.4 float formatting: %.14g, integer-valued floats keep a trailing .0
+    -- -------------------------------------------------------------------------
+    if tostring(1.0) ~= "1.0" then return 60 end
+    if tostring(100.0) ~= "100.0" then return 61 end
+    if tostring(-0.0) ~= "-0.0" then return 62 end
+    if tostring(0.1) ~= "0.1" then return 63 end
+    if tostring(1e20) ~= "1e+20" then return 64 end
+    if tostring(1 / 0) ~= "inf" then return 65 end
+    -- sign of NaN is platform-dependent in Lua too
+    local nan_str = tostring(0 / 0)
+    if nan_str ~= "nan" and nan_str ~= "-nan" then return 66 end
+
+    -- String concatenation uses the same formatting
+    if ("x" .. 1.0) ~= "x1.0" then return 67 end
+    if (1.0 .. "") ~= "1.0" then return 68 end
+
+    -- Round-trip must preserve the float subtype
+    if math.type(tonumber(tostring(1.0))) ~= "float" then return 69 end
+
+    -- table.concat numbers follows the same rule
+    if table.concat({ 1.0, 2.5, 3 }, ",") ~= "1.0,2.5,3" then return 70 end
+
     return 5000
 end
diff --git a/test/lua/string/test_format_s_bad_arg.lua b/test/lua/string/test_format_s_bad_arg.lua
deleted file mode 100644
index 3c8e748..0000000
--- a/test/lua/string/test_format_s_bad_arg.lua
+++ /dev/null
@@ -1,5 +0,0 @@
-function test_format_s_bad_arg()
-    -- string.format "%s" format requires a string/number argument; Bool is invalid per standard Lua
-    string.format("%s", true)
-    return 0
-end
diff --git a/test/lua/string/test_format_s_types.lua b/test/lua/string/test_format_s_types.lua
new file mode 100644
index 0000000..14afa6e
--- /dev/null
+++ b/test/lua/string/test_format_s_types.lua
@@ -0,0 +1,23 @@
+-- Lua 5.4: string.format("%s", x) 等价于对 x 调用 tostring（luaL_tolstring）：
+-- string/number/bool/nil 均合法，只有 table（无 __tostring 元方法）报错。
+function test_format_s_types()
+    if string.format("%s", true) ~= "true" then return 1 end
+    if string.format("%s", false) ~= "false" then return 2 end
+    if string.format("%s", nil) ~= "nil" then return 3 end
+    if string.format("%s", 42) ~= "42" then return 4 end
+    -- float 走 Lua 数字格式，而不是 C 的 6 位小数
+    if string.format("%s", 2.5) ~= "2.5" then return 5 end
+    if string.format("%s", 1.0) ~= "1.0" then return 6 end
+    if string.format("%s", 1e20) ~= "1e+20" then return 7 end
+    if string.format("[%s]", 2.5) ~= "[2.5]" then return 8 end
+    -- 宽度/对齐修饰仍作用于 tostring 的结果
+    if string.format("%-6s|", "ab") ~= "ab    |" then return 9 end
+    -- string 原样返回
+    if string.format("%s", "hi") ~= "hi" then return 10 end
+
+    -- table 没有 __tostring，仍然报错
+    local ok = pcall(function() return string.format("%s", { 1, 2 }) end)
+    if ok then return 11 end
+
+    return 5000
+end
diff --git a/test/lua/string/test_gsub_negative_n.lua b/test/lua/string/test_gsub_negative_n.lua
new file mode 100644
index 0000000..6742c6b
--- /dev/null
+++ b/test/lua/string/test_gsub_negative_n.lua
@@ -0,0 +1,29 @@
+-- Lua 5.4: gsub 第四参缺省/nil 时为 srcl+1（不限次数）；显式传入的负数或 0
+-- 意味着一次都不替换（while (n < max_s)），而不是"不限次数"。
+function test_gsub_negative_n()
+    local r1, c1 = ("aaa"):gsub("a", "X", -1)
+    if r1 ~= "aaa" or c1 ~= 0 then return 1 end
+
+    local r2, c2 = ("hello"):gsub("l", "L", -2)
+    if r2 ~= "hello" or c2 ~= 0 then return 2 end
+
+    local r3, c3 = ("aaa"):gsub("a", "X", 0)
+    if r3 ~= "aaa" or c3 ~= 0 then return 3 end
+
+    local r4, c4 = ("aaa"):gsub("a", "X", 2)
+    if r4 ~= "XXa" or c4 ~= 2 then return 4 end
+
+    -- 缺省：全部替换
+    local r5, c5 = ("aaa"):gsub("a", "X")
+    if r5 ~= "XXX" or c5 ~= 3 then return 5 end
+
+    -- 显式 nil 与缺省等价
+    local r6, c6 = ("aaa"):gsub("a", "X", nil)
+    if r6 ~= "XXX" or c6 ~= 3 then return 6 end
+
+    -- 大于匹配总数的值等同于全部替换
+    local r7, c7 = ("aaa"):gsub("a", "X", 100)
+    if r7 ~= "XXX" or c7 ~= 3 then return 7 end
+
+    return 5000
+end
diff --git a/test/test_string.cpp b/test/test_string.cpp
index 505e902..4a39352 100644
--- a/test/test_string.cpp
+++ b/test/test_string.cpp
@@ -430,16 +430,30 @@ TEST(test_string, test_gsub_bad_func_return_bool) {
     FakeluaDeleteState(s);
 }
 
-TEST(test_string, test_format_s_bad_arg) {
+TEST(test_string, test_format_s_types) {
     State *s = FakeluaNewState();
     ASSERT_NE(s, nullptr);
     CompileConfig config;
 
-    CompileFile(s, "./string/test_format_s_bad_arg.lua", config);
+    CompileFile(s, "./string/test_format_s_types.lua", config);
 
-    // TCC 是 C 编译器，不支持 C++ 异常传播，只测试 GCC 后端
-    double res = 0;
-    CallThrow(s, "test_format_s_bad_arg", res);
+    int64_t res = 0;
+    CallAll(s, "test_format_s_types", res);
+    EXPECT_EQ(res, 5000);
+
+    FakeluaDeleteState(s);
+}
+
+TEST(test_string, test_gsub_negative_n) {
+    State *s = FakeluaNewState();
+    ASSERT_NE(s, nullptr);
+    CompileConfig config;
+
+    CompileFile(s, "./string/test_gsub_negative_n.lua", config);
+
+    int64_t res = 0;
+    CallAll(s, "test_gsub_negative_n", res);
+    EXPECT_EQ(res, 5000);
 
     FakeluaDeleteState(s);
 }
diff --git a/test/test_var.cpp b/test/test_var.cpp
index 730934f..bedaaba 100644
--- a/test/test_var.cpp
+++ b/test/test_var.cpp
@@ -120,7 +120,7 @@ TEST(var, ToString) {
     ASSERT_EQ(v.ToString(), "12345");
 
     v.SetFloat(12345.0);
-    ASSERT_EQ(v.ToString(), "12345");
+    ASSERT_EQ(v.ToString(), "12345.0");
 
     v.SetFloat(12345.1);
     ASSERT_EQ(v.ToString(), "12345.1");