From 05e7f0977561a3f432db868eae4800cb3ab6be6f Mon Sep 17 00:00:00 2001 From: Victor Stinner Date: Fri, 17 Sep 2021 16:37:05 +0200 Subject: [PATCH] bpo-45116: Py_DEBUG ignores Py_ALWAYS_INLINE If the Py_DEBUG macro is defined, the Py_ALWAYS_INLINE macro does nothing. --- Doc/c-api/intro.rst | 3 +++ Include/pyport.h | 11 ++++++++++- 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/Doc/c-api/intro.rst b/Doc/c-api/intro.rst index aac28b1e77561a..3e7890cb766471 100644 --- a/Doc/c-api/intro.rst +++ b/Doc/c-api/intro.rst @@ -124,6 +124,9 @@ complete listing. worse performances (due to increased code size for example). The compiler is usually smarter than the developer for the cost/benefit analysis. + If Python is :ref:`built in debug mode ` (if the ``Py_DEBUG`` + macro is defined), the :c:macro:`Py_ALWAYS_INLINE` macro does nothing. + It must be specified before the function return type. Usage:: static inline Py_ALWAYS_INLINE int random(void) { return 4; } diff --git a/Include/pyport.h b/Include/pyport.h index af7fbe7fc71954..d27d0838f1b2cb 100644 --- a/Include/pyport.h +++ b/Include/pyport.h @@ -568,10 +568,19 @@ extern "C" { // worse performances (due to increased code size for example). The compiler is // usually smarter than the developer for the cost/benefit analysis. // +// If Python is built in debug mode (if the Py_DEBUG macro is defined), the +// Py_ALWAYS_INLINE macro does nothing. +// // It must be specified before the function return type. Usage: // // static inline Py_ALWAYS_INLINE int random(void) { return 4; } -#if defined(__GNUC__) || defined(__clang__) || defined(__INTEL_COMPILER) +#if defined(Py_DEBUG) + // If Python is built in debug mode, usually compiler optimizations are + // disabled. In this case, Py_ALWAYS_INLINE can increase a lot the stack + // memory usage. For example, forcing inlining using gcc -O0 increases the + // stack usage from 6 KB to 15 KB per Python function call. +# define Py_ALWAYS_INLINE +#elif defined(__GNUC__) || defined(__clang__) || defined(__INTEL_COMPILER) # define Py_ALWAYS_INLINE __attribute__((always_inline)) #elif defined(_MSC_VER) # define Py_ALWAYS_INLINE __forceinline