Merge branch 'main' into issue_165161

Author: RKSimon

clang/docs/Modules.rst

@@ -421,13 +421,7 @@ As an example, the module map file for the C standard library might look a bit l
 
 .. parsed-literal::
 
-  module std [system] [extern_c] {
-    module assert {
-      textual header "assert.h"
-      header "bits/assert-decls.h"
-      export *
-    }
-
+  module std [system] {
     module complex {
       header "complex.h"
       export *
@@ -440,7 +434,6 @@ As an example, the module map file for the C standard library might look a bit l
 
     module errno {
       header "errno.h"
-      header "sys/errno.h"
       export *
     }
 
@@ -673,14 +666,14 @@ of checking *use-declaration*\s, and must still be a lexically-valid header
 file. In the future, we intend to pre-tokenize such headers and include the
 token sequence within the prebuilt module representation.
 
-A header with the ``exclude`` specifier is excluded from the module. It will not be included when the module is built, nor will it be considered to be part of the module, even if an ``umbrella`` header or directory would otherwise make it part of the module.
+A header with the ``exclude`` specifier is excluded from the module. It will not be included when the module is built, nor will it be considered to be part of the module, even if an ``umbrella`` directory would otherwise make it part of the module.
 
-**Example:** The C header ``assert.h`` is an excellent candidate for a textual header, because it is meant to be included multiple times (possibly with different ``NDEBUG`` settings). However, declarations within it should typically be split into a separate modular header.
+**Example:** A "X macro" header is an excellent candidate for a textual header, because it is can't be compiled standalone, and by itself does not contain any declarations.
 
 .. parsed-literal::
 
-  module std [system] {
-    textual header "assert.h"
+  module MyLib [system] {
+    textual header "xmacros.h"
   }
 
 A given header shall not be referenced by more than one *header-declaration*.

libc/CMakeLists.txt

@@ -363,7 +363,7 @@ elseif(LLVM_LIBC_FULL_BUILD)
   message(FATAL_ERROR "${LIBC_CONFIG_PATH}/headers.txt file not found and fullbuild requested.")
 endif()
 
-# Check exclude.txt that appends to LIBC_EXCLUDE_ENTRYPOINTS list
+# Check exclude.txt that appends to TARGET_LLVMLIBC_REMOVED_ENTRYPOINTS list
 if(EXISTS "${LIBC_CONFIG_PATH}/exclude.txt")
     include("${LIBC_CONFIG_PATH}/exclude.txt")
 endif()

libc/config/linux/x86_64/exclude.txt

@@ -19,3 +19,11 @@ if(NOT has_sys_random)
     )
   endif()
 endif()
+
+include(CheckSymbolExists)
+check_symbol_exists(SYS_faccessat2 "sys/syscall.h" HAVE_SYS_FACCESSAT2)
+if(NOT HAVE_SYS_FACCESSAT2)
+  list(APPEND TARGET_LLVMLIBC_REMOVED_ENTRYPOINTS
+    libc.src.unistd.faccessat
+  )
+endif()

libc/src/time/strftime.cpp

@@ -26,7 +26,7 @@ LLVM_LIBC_FUNCTION(size_t, strftime,
   int ret = strftime_core::strftime_main(&writer, format, timeptr);
   if (buffsz > 0) // if the buffsz is 0 the buffer may be a null pointer.
     wb.buff[wb.buff_cur] = '\0';
-  return (ret < 0 || static_cast<size_t>(ret) > buffsz) ? 0 : ret;
+  return (ret < 0 || static_cast<size_t>(ret) >= buffsz) ? 0 : ret;
 }
 
 } // namespace LIBC_NAMESPACE_DECL

libc/src/time/strftime_l.cpp

@@ -29,7 +29,7 @@ LLVM_LIBC_FUNCTION(size_t, strftime_l,
   int ret = strftime_core::strftime_main(&writer, format, timeptr);
   if (buffsz > 0) // if the buffsz is 0 the buffer may be a null pointer.
     wb.buff[wb.buff_cur] = '\0';
-  return (ret < 0 || static_cast<size_t>(ret) > buffsz) ? 0 : ret;
+  return (ret < 0 || static_cast<size_t>(ret) >= buffsz) ? 0 : ret;
 }
 
 } // namespace LIBC_NAMESPACE_DECL

libc/test/src/time/strftime_test.cpp

@@ -2326,3 +2326,23 @@ TEST(LlvmLibcStrftimeTest, TimeFormatFullDateTime) {
 //    size_t written = 0;
 //    SimplePaddedNum spn;
 //  }
+
+TEST(LlvmLibcStrftimeTest, BufferTooSmall) {
+  struct tm time;
+  char buffer[1];
+
+  time.tm_year = get_adjusted_year(2025);
+  time.tm_mon = 10;
+  time.tm_mday = 24;
+
+  size_t written =
+      LIBC_NAMESPACE::strftime(buffer, sizeof(buffer), "%F", &time);
+  EXPECT_EQ(written, size_t{0});
+
+  char buffer2[10];
+
+  // The string "2025-11-24" is 10 chars,
+  // so strftime needs 10 + 1 bytes to write the string and the null terminator.
+  written = LIBC_NAMESPACE::strftime(buffer, sizeof(buffer2), "%F", &time);
+  EXPECT_EQ(written, size_t{0});
+}