From 2f539596c6e9a977e91b6bc6344650422c6bc3b0 Mon Sep 17 00:00:00 2001
From: Georgi Gerganov <ggerganov@gmail.com>
Date: Mon, 14 Sep 2026 13:03:41 +0300
Subject: [PATCH] ggml-cpu : disable PCH and fix CACHE_LINE_SIZE ambiguity to
 fix heap corruption (#28882)

Disable the ggml-cpu precompiled header and remove the
std::hardware_destructive_interference_size branch from CACHE_LINE_SIZE.

The PCH force-includes ggml-impl.h before ops.h, which pulls in <new>
via <array>/<vector> and defines __cpp_lib_hardware_interference_size.
This makes the C++ kernels use CACHE_LINE_SIZE = 256 (hardware
destructive interference size) while the C work-buffer sizing code in
ggml-cpu.c always uses the fallback 64. The mismatch undersizes the
rope work buffer by (CACHE_LINE_SIZE/4 - 16) * n_threads * 4 bytes,
causing a heap-buffer-overflow that corrupts the heap and later crashes
in ggml_compute_forward_rope_flt.

Disabling the ggml-cpu PCH restores the natural include order so
ops.h is processed before <new>, keeping CACHE_LINE_SIZE consistent.
Removing the std::hardware_destructive_interference_size branch makes
the value deterministic and include-order independent.

ref: https://github.com/ggml-org/llama.cpp/issues/28858

Assisted-by: pi:llama.cpp/DeepSeek-V4-Flash-Vision-Exp
---
 ggml/src/ggml-cpu/CMakeLists.txt |  6 ------
 ggml/src/ggml-cpu/ops.h          | 17 ++++-------------
 2 files changed, 4 insertions(+), 19 deletions(-)

diff --git a/ggml/src/ggml-cpu/CMakeLists.txt b/ggml/src/ggml-cpu/CMakeLists.txt
index 83088e147..1c7338eea 100644
--- a/ggml/src/ggml-cpu/CMakeLists.txt
+++ b/ggml/src/ggml-cpu/CMakeLists.txt
@@ -675,12 +675,6 @@ function(ggml_add_cpu_backend_variant_impl tag_name)
     target_compile_options(${GGML_CPU_NAME} PRIVATE ${ARCH_FLAGS})
     target_compile_definitions(${GGML_CPU_NAME} PRIVATE ${ARCH_DEFINITIONS})
 
-    if (CMAKE_C_COMPILER_ID STREQUAL "GNU" AND NOT GGML_SYSTEM_ARCH STREQUAL "x86")
-        message(STATUS "Skipping PCH for ${GGML_CPU_NAME}: GCC PCH is only enabled for x86 (arch: ${GGML_SYSTEM_ARCH})")
-    else()
-        target_precompile_headers(${GGML_CPU_NAME} PRIVATE ggml-impl.h)
-    endif()
-
     if (EMSCRIPTEN)
         set_target_properties(${GGML_CPU_NAME} PROPERTIES COMPILE_FLAGS "-msimd128")
     endif()
diff --git a/ggml/src/ggml-cpu/ops.h b/ggml/src/ggml-cpu/ops.h
index ce2b3e870..2728b08b6 100644
--- a/ggml/src/ggml-cpu/ops.h
+++ b/ggml/src/ggml-cpu/ops.h
@@ -5,10 +5,10 @@
 //
 // cache line
 //
-
-#if defined(__cpp_lib_hardware_interference_size)
-#define CACHE_LINE_SIZE std::hardware_destructive_interference_size
-#else
+// TODO: rework CACHE_LINE_SIZE so std::hardware_destructive_interference_size
+// can be used consistently between C and C++ TUs; the previous macro form
+// diverged based on include order and undersized the work buffer.
+// ref: https://github.com/ggml-org/llama.cpp/pull/28882
 #if defined(__POWER9_VECTOR__)
 #define CACHE_LINE_SIZE 128
 #elif defined(__VXE__) || defined(__VXE2__)
@@ -16,17 +16,8 @@
 #else
 #define CACHE_LINE_SIZE 64
 #endif
-#endif
 
-// -Winterference-size was introduced in GCC 12
-#if defined(__cplusplus) && defined(__GNUC__) && !defined(__clang__) && __GNUC__ >= 12
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Winterference-size"
-#endif
 static const size_t CACHE_LINE_SIZE_F32 = CACHE_LINE_SIZE/sizeof(float);
-#if defined(__cplusplus) && defined(__GNUC__) && !defined(__clang__) && __GNUC__ >= 12
-#pragma GCC diagnostic pop
-#endif
 
 // Work buffer size for im2col operations in CONV2D
 #define GGML_IM2COL_WORK_SIZE (16 * 1024 * 1024)