[libc-commits] [libc] [libc] Define SSIZE_MAX in limits-macros.h (PR #201087)

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llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: Jeff Bailey (kaladron)

<details>
<summary>Changes</summary>

Defined SSIZE_MAX in limits-macros.h to support POSIX compliance. Applications compiling against LLVM libc require SSIZE_MAX to be defined in limits.h.

SSIZE_MAX is defined strictly in terms of __PTRDIFF_MAX__, matching ssize_t defined as __PTRDIFF_TYPE__, ensuring they are always structurally aligned and compile-time safe.

Added Doxygen comments for SSIZE_MAX.
Added SSIZE_MAX to limits.yaml and added a unit test in limits_test.cpp to verify the definition.

Assisted-by: Automated tooling, human reviewed.

---
Full diff: https://github.com/llvm/llvm-project/pull/201087.diff


3 Files Affected:

- (modified) libc/include/limits.yaml (+2) 
- (modified) libc/include/llvm-libc-macros/limits-macros.h (+7) 
- (modified) libc/test/src/__support/CPP/limits_test.cpp (+8) 


``````````diff
diff --git a/libc/include/limits.yaml b/libc/include/limits.yaml
index 0f16d87f67a70..25dd6bf2395da 100644
--- a/libc/include/limits.yaml
+++ b/libc/include/limits.yaml
@@ -84,6 +84,8 @@ macros:
     macro_header: limits-macros.h
   - macro_name: PTHREAD_DESTRUCTOR_ITERATIONS
     macro_header: limits-macros.h
+  - macro_name: SSIZE_MAX
+    macro_header: limits-macros.h
 types: []
 enums: []
 objects: []
diff --git a/libc/include/llvm-libc-macros/limits-macros.h b/libc/include/llvm-libc-macros/limits-macros.h
index b4e22fa7b239a..3de4ad2e7c245 100644
--- a/libc/include/llvm-libc-macros/limits-macros.h
+++ b/libc/include/llvm-libc-macros/limits-macros.h
@@ -261,4 +261,11 @@
 #define IOV_MAX 1024
 #endif // IOV_MAX
 
+#ifndef SSIZE_MAX
+#ifdef __PTRDIFF_MAX__
+/// The maximum value that can be stored in an object of type ssize_t.
+#define SSIZE_MAX __PTRDIFF_MAX__
+#endif
+#endif
+
 #endif // LLVM_LIBC_MACROS_LIMITS_MACROS_H
diff --git a/libc/test/src/__support/CPP/limits_test.cpp b/libc/test/src/__support/CPP/limits_test.cpp
index 6c94b091f15bf..8f507bfb2ef60 100644
--- a/libc/test/src/__support/CPP/limits_test.cpp
+++ b/libc/test/src/__support/CPP/limits_test.cpp
@@ -31,6 +31,14 @@ TEST(LlvmLibcLimitsTest, LimitsFollowSpec) {
   ASSERT_EQ(cpp::numeric_limits<long long>::min(), LLONG_MIN);
 
   ASSERT_EQ(cpp::numeric_limits<unsigned long long>::max(), ULLONG_MAX);
+
+#ifdef SSIZE_MAX
+  ASSERT_EQ(cpp::numeric_limits<__PTRDIFF_TYPE__>::max(), SSIZE_MAX);
+#else
+#ifdef LIBC_FULL_BUILD
+#error "SSIZE_MAX is not defined in full build mode"
+#endif
+#endif
 }
 
 TEST(LlvmLibcLimitsTest, UInt128Limits) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/201087