From e4c0595ec4ed3cd2f6fb471081a9d2d3960e1672 Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Mon, 7 Oct 2024 21:25:22 +0200
Subject: [PATCH] libcpp: Use constexpr for _cpp_trigraph_map initialization
for C++14
The _cpp_trigraph_map initialization used to be done for C99+ using
designated initializers, but can't be done that way for C++ because
the designated initializer support in C++ as array designators are just
an extension there and don't allow skipping anything nor going backwards.
But, we can get the same effect using C++14 constexpr constructor.
With the following patch we get rid of the runtime initialization
and the array can be in .rodata.
2024-10-07 Jakub Jelinek <jakub@redhat.com>
* internal.h (_cpp_trigraph_map_s): New type for C++14 or later.
(_cpp_trigraph_map_d): New variable for C++14 or later.
(_cpp_trigraph_map): Define to _cpp_trigraph_map_d.map for C++14 or
later.
* init.cc (init_trigraph_map): Define to nothing for C++14 or later.
(TRIGRAPH_MAP, END, s): Define differently for C++14 or later.
---
libcpp/init.cc | 13 +++++++++++--
libcpp/internal.h | 6 ++++++
2 files changed, 17 insertions(+), 2 deletions(-)
diff --git a/libcpp/init.cc b/libcpp/init.cc
index 2c80d63a491d..3e4a2bc0ae79 100644
--- a/libcpp/init.cc
+++ b/libcpp/init.cc
@@ -41,8 +41,8 @@ static void read_original_directory (cpp_reader *);
static void post_options (cpp_reader *);
/* If we have designated initializers (GCC >2.7) these tables can be
- initialized, constant data. Otherwise, they have to be filled in at
- runtime. */
+ initialized, constant data. Similarly for C++14 and later.
+ Otherwise, they have to be filled in at runtime. */
#if HAVE_DESIGNATED_INITIALIZERS
#define init_trigraph_map() /* Nothing. */
@@ -52,6 +52,15 @@ __extension__ const uchar _cpp_trigraph_map[UCHAR_MAX + 1] = {
#define END };
#define s(p, v) [p] = v,
+#elif __cpp_constexpr >= 201304L
+
+#define init_trigraph_map() /* Nothing. */
+#define TRIGRAPH_MAP \
+constexpr _cpp_trigraph_map_s::_cpp_trigraph_map_s () : map {} {
+#define END } \
+constexpr _cpp_trigraph_map_s _cpp_trigraph_map_d;
+#define s(p, v) map[p] = v;
+
#else
#define TRIGRAPH_MAP uchar _cpp_trigraph_map[UCHAR_MAX + 1] = { 0 }; \
diff --git a/libcpp/internal.h b/libcpp/internal.h
index b69a0377f024..2379fbba8996 100644
--- a/libcpp/internal.h
+++ b/libcpp/internal.h
@@ -668,6 +668,12 @@ struct cpp_embed_params
compiler that supports C99. */
#if HAVE_DESIGNATED_INITIALIZERS
extern const unsigned char _cpp_trigraph_map[UCHAR_MAX + 1];
+#elif __cpp_constexpr >= 201304L
+extern const struct _cpp_trigraph_map_s {
+ unsigned char map[UCHAR_MAX + 1];
+ constexpr _cpp_trigraph_map_s ();
+} _cpp_trigraph_map_d;
+#define _cpp_trigraph_map _cpp_trigraph_map_d.map
#else
extern unsigned char _cpp_trigraph_map[UCHAR_MAX + 1];
#endif
--
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