https://github.com/zeyi2 updated 
https://github.com/llvm/llvm-project/pull/208135

>From 6bacea1432e5e8862afb8826d30fa401f44c50d0 Mon Sep 17 00:00:00 2001
From: Zeyi Xu <[email protected]>
Date: Wed, 8 Jul 2026 11:14:17 +0800
Subject: [PATCH 1/2] [Clang] Define __WCHAR_MIN__ and related macros

---
 clang/lib/Frontend/InitPreprocessor.cpp | 11 +++++++++++
 clang/test/Preprocessor/init-aarch64.c  |  3 +++
 clang/test/Preprocessor/init-riscv.c    |  8 ++++++++
 clang/test/Preprocessor/init.c          |  4 ++++
 4 files changed, 26 insertions(+)

diff --git a/clang/lib/Frontend/InitPreprocessor.cpp 
b/clang/lib/Frontend/InitPreprocessor.cpp
index 7752ab5131aae..8b6ff844d0daa 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -186,6 +186,14 @@ static void DefineTypeSize(const Twine &MacroName, 
TargetInfo::IntType Ty,
                  TI.isTypeSigned(Ty), Builder);
 }
 
+static void DefineTypeMin(const Twine &Prefix, TargetInfo::IntType Ty,
+                          const TargetInfo &TI, MacroBuilder &Builder) {
+  Builder.defineMacro(Prefix + "_MIN__",
+                      TI.isTypeSigned(Ty)
+                          ? Twine("(-") + Prefix + "_MAX__ - 1)"
+                          : Twine("0") + TI.getTypeConstantSuffix(Ty));
+}
+
 static void DefineFmt(const LangOptions &LangOpts, const Twine &Prefix,
                       TargetInfo::IntType Ty, const TargetInfo &TI,
                       MacroBuilder &Builder) {
@@ -1129,7 +1137,9 @@ static void InitializePredefinedMacros(const TargetInfo 
&TI,
   DefineTypeSize("__LONG_MAX__", TargetInfo::SignedLong, TI, Builder);
   DefineTypeSize("__LONG_LONG_MAX__", TargetInfo::SignedLongLong, TI, Builder);
   DefineTypeSizeAndWidth("__WCHAR", TI.getWCharType(), TI, Builder);
+  DefineTypeMin("__WCHAR", TI.getWCharType(), TI, Builder);
   DefineTypeSizeAndWidth("__WINT", TI.getWIntType(), TI, Builder);
+  DefineTypeMin("__WINT", TI.getWIntType(), TI, Builder);
   DefineTypeSizeAndWidth("__INTMAX", TI.getIntMaxType(), TI, Builder);
   DefineTypeSizeAndWidth("__SIZE", TI.getSizeType(), TI, Builder);
 
@@ -1182,6 +1192,7 @@ static void InitializePredefinedMacros(const TargetInfo 
&TI,
   DefineType("__WCHAR_TYPE__", TI.getWCharType(), Builder);
   DefineType("__WINT_TYPE__", TI.getWIntType(), Builder);
   DefineTypeSizeAndWidth("__SIG_ATOMIC", TI.getSigAtomicType(), TI, Builder);
+  DefineTypeMin("__SIG_ATOMIC", TI.getSigAtomicType(), TI, Builder);
   if (LangOpts.C23)
     DefineType("__CHAR8_TYPE__", TI.UnsignedChar, Builder);
   DefineType("__CHAR16_TYPE__", TI.getChar16Type(), Builder);
diff --git a/clang/test/Preprocessor/init-aarch64.c 
b/clang/test/Preprocessor/init-aarch64.c
index 09e3fc926a309..f875c10775e29 100644
--- a/clang/test/Preprocessor/init-aarch64.c
+++ b/clang/test/Preprocessor/init-aarch64.c
@@ -263,6 +263,7 @@
 // AARCH64-NEXT: #define __SHRT_MAX__ 32767
 // AARCH64-NEXT: #define __SHRT_WIDTH__ 16
 // AARCH64-NEXT: #define __SIG_ATOMIC_MAX__ 2147483647
+// AARCH64-NEXT: #define __SIG_ATOMIC_MIN__ (-__SIG_ATOMIC_MAX__ - 1)
 // AARCH64-NEXT: #define __SIG_ATOMIC_WIDTH__ 32
 // AARCH64-NEXT: #define __SIZEOF_DOUBLE__ 8
 // AARCH64-NEXT: #define __SIZEOF_FLOAT__ 4
@@ -393,10 +394,12 @@
 // AARCH64-NEXT: #define __USER_LABEL_PREFIX__
 // AARCH64-NEXT: #define __VERSION__ "{{.*}}"
 // AARCH64-NEXT: #define __WCHAR_MAX__ 4294967295U
+// AARCH64-NEXT: #define __WCHAR_MIN__ 0U
 // AARCH64-NEXT: #define __WCHAR_TYPE__ unsigned int
 // AARCH64-NEXT: #define __WCHAR_UNSIGNED__ 1
 // AARCH64-NEXT: #define __WCHAR_WIDTH__ 32
 // AARCH64-NEXT: #define __WINT_MAX__ 2147483647
+// AARCH64-NEXT: #define __WINT_MIN__ (-__WINT_MAX__ - 1)
 // AARCH64-NEXT: #define __WINT_TYPE__ int
 // AARCH64-NEXT: #define __WINT_WIDTH__ 32
 // AARCH64-NEXT: #define __aarch64__ 1
diff --git a/clang/test/Preprocessor/init-riscv.c 
b/clang/test/Preprocessor/init-riscv.c
index 4eeecccff4378..00282e670a0f7 100644
--- a/clang/test/Preprocessor/init-riscv.c
+++ b/clang/test/Preprocessor/init-riscv.c
@@ -2,9 +2,17 @@
 // RUN:     FileCheck -match-full-lines -check-prefixes=RV32 %s
 // RUN: %clang_cc1 -E -dM -triple=riscv64 < /dev/null | \
 // RUN:     FileCheck -match-full-lines -check-prefixes=RV64 %s
+// RUN: %clang_cc1 -E -dM -triple=riscv32-unknown-netbsd < /dev/null | \
+// RUN:     FileCheck -match-full-lines -check-prefixes=NETBSD %s
+// RUN: %clang_cc1 -E -dM -triple=riscv64-unknown-netbsd < /dev/null | \
+// RUN:     FileCheck -match-full-lines -check-prefixes=NETBSD %s
 
 // RV32: #define __GCC_CONSTRUCTIVE_SIZE 64
 // RV32: #define __GCC_DESTRUCTIVE_SIZE 64
 
 // RV64: #define __GCC_CONSTRUCTIVE_SIZE 64
 // RV64: #define __GCC_DESTRUCTIVE_SIZE 64
+
+// NETBSD: #define __SIG_ATOMIC_MIN__ (-__SIG_ATOMIC_MAX__ - 1)
+// NETBSD: #define __WCHAR_MIN__ (-__WCHAR_MAX__ - 1)
+// NETBSD: #define __WINT_MIN__ 0U
diff --git a/clang/test/Preprocessor/init.c b/clang/test/Preprocessor/init.c
index ef7b76a29a1f5..afea10ea2a38f 100644
--- a/clang/test/Preprocessor/init.c
+++ b/clang/test/Preprocessor/init.c
@@ -1949,8 +1949,10 @@
 // WEBASSEMBLY-NEXT:#define __SHRT_MAX__ 32767
 // WEBASSEMBLY-NEXT:#define __SHRT_WIDTH__ 16
 // WEBASSEMBLY32-NEXT:#define __SIG_ATOMIC_MAX__ 2147483647L
+// WEBASSEMBLY32-NEXT:#define __SIG_ATOMIC_MIN__ (-__SIG_ATOMIC_MAX__ - 1)
 // WEBASSEMBLY32-NEXT:#define __SIG_ATOMIC_WIDTH__ 32
 // WEBASSEMBLY64-NEXT:#define __SIG_ATOMIC_MAX__ 9223372036854775807L
+// WEBASSEMBLY64-NEXT:#define __SIG_ATOMIC_MIN__ (-__SIG_ATOMIC_MAX__ - 1)
 // WEBASSEMBLY64-NEXT:#define __SIG_ATOMIC_WIDTH__ 64
 // WEBASSEMBLY-NEXT:#define __SIZEOF_DOUBLE__ 8
 // WEBASSEMBLY-NEXT:#define __SIZEOF_FLOAT__ 4
@@ -2092,10 +2094,12 @@
 // WEBASSEMBLY-NEXT:#define __USER_LABEL_PREFIX__
 // WEBASSEMBLY-NEXT:#define __VERSION__ "{{.*}}"
 // WEBASSEMBLY-NEXT:#define __WCHAR_MAX__ 2147483647
+// WEBASSEMBLY-NEXT:#define __WCHAR_MIN__ (-__WCHAR_MAX__ - 1)
 // WEBASSEMBLY-NEXT:#define __WCHAR_TYPE__ int
 // WEBASSEMBLY-NOT:#define __WCHAR_UNSIGNED__
 // WEBASSEMBLY-NEXT:#define __WCHAR_WIDTH__ 32
 // WEBASSEMBLY-NEXT:#define __WINT_MAX__ 2147483647
+// WEBASSEMBLY-NEXT:#define __WINT_MIN__ (-__WINT_MAX__ - 1)
 // WEBASSEMBLY-NEXT:#define __WINT_TYPE__ int
 // WEBASSEMBLY-NOT:#define __WINT_UNSIGNED__
 // WEBASSEMBLY-NEXT:#define __WINT_WIDTH__ 32

>From ad2b9d96ee5c5279e16a2d25eb5e7202d57d9959 Mon Sep 17 00:00:00 2001
From: Zeyi Xu <[email protected]>
Date: Wed, 8 Jul 2026 23:33:45 +0800
Subject: [PATCH 2/2] address feedback :)

---
 clang/docs/ReleaseNotes.md |  1 +
 clang/lib/Headers/stdint.h | 19 +++++--------------
 2 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md
index e12ae0b2eeed4..1811a0e2a9a42 100644
--- a/clang/docs/ReleaseNotes.md
+++ b/clang/docs/ReleaseNotes.md
@@ -781,6 +781,7 @@ latest release, please see the [Clang Web 
Site](https://clang.llvm.org) or the
 - Fixed assertion failures involving code completion with delayed default 
arguments and exception specifications. (#GH200879)
 - Fixed a regression where calling a function that takes a class-type 
parameter by value inside `decltype` of a concept could be incorrectly rejected 
when used as a non-type template argument. (#GH175831)
 - Fixed a crash in the constant evaluator when an ill-formed array 
new-expression whose bound could not be determined (e.g. `new int[]()`) was 
used in a constant expression. (#GH200139)
+- Clang now defines the GCC-compatible predefined macros `__WCHAR_MIN__`, 
`__WINT_MIN__`, and `__SIG_ATOMIC_MIN__`. (#GH199678)
 
 #### Bug Fixes to Compiler Builtins
 
diff --git a/clang/lib/Headers/stdint.h b/clang/lib/Headers/stdint.h
index 96c2ccace13d0..2471b6e3860a4 100644
--- a/clang/lib/Headers/stdint.h
+++ b/clang/lib/Headers/stdint.h
@@ -805,25 +805,16 @@ typedef __UINTMAX_TYPE__ uintmax_t;
 #endif
 
 /* C99 7.18.3 Limits of other integer types. */
-#define SIG_ATOMIC_MIN __INTN_MIN(__SIG_ATOMIC_WIDTH__)
-#define SIG_ATOMIC_MAX __INTN_MAX(__SIG_ATOMIC_WIDTH__)
-#ifdef __WINT_UNSIGNED__
-# define WINT_MIN       __UINTN_C(__WINT_WIDTH__, 0)
-# define WINT_MAX       __UINTN_MAX(__WINT_WIDTH__)
-#else
-# define WINT_MIN       __INTN_MIN(__WINT_WIDTH__)
-# define WINT_MAX       __INTN_MAX(__WINT_WIDTH__)
-#endif
+#define SIG_ATOMIC_MIN __SIG_ATOMIC_MIN__
+#define SIG_ATOMIC_MAX __SIG_ATOMIC_MAX__
+#define WINT_MIN       __WINT_MIN__
+#define WINT_MAX       __WINT_MAX__
 
 #ifndef WCHAR_MAX
 # define WCHAR_MAX __WCHAR_MAX__
 #endif
 #ifndef WCHAR_MIN
-# if __WCHAR_MAX__ == __INTN_MAX(__WCHAR_WIDTH__)
-#  define WCHAR_MIN __INTN_MIN(__WCHAR_WIDTH__)
-# else
-#  define WCHAR_MIN __UINTN_C(__WCHAR_WIDTH__, 0)
-# endif
+# define WCHAR_MIN __WCHAR_MIN__
 #endif
 
 /* 7.18.4.2 Macros for greatest-width integer constants. */

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