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* [gcc r13-3707] libstdc++: Move stream initialization into compiled library [PR44952]
@ 2022-11-06 16:16 Patrick Palka
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From: Patrick Palka @ 2022-11-06 16:16 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:4e4e3ffd10f53ef71696bc728ab40258751a2df4
commit r13-3707-g4e4e3ffd10f53ef71696bc728ab40258751a2df4
Author: Patrick Palka <ppalka@redhat.com>
Date: Sun Nov 6 11:16:00 2022 -0500
libstdc++: Move stream initialization into compiled library [PR44952]
This patch moves the static object for constructing the standard streams
out from <iostream> and into the compiled library on systems that support
init priorities. This'll mean <iostream> no longer introduces a separate
global constructor in each TU that includes it.
We can do this only if the init_priority attribute is supported because
we need a way to ensure the stream initialization runs first before any
user global initializer, particularly when linking with a static
libstdc++.a.
PR libstdc++/44952
PR libstdc++/39796
PR libstdc++/98108
libstdc++-v3/ChangeLog:
* include/std/iostream (__ioinit): No longer define here if
the init_priority attribute is usable.
* src/c++98/ios_init.cc (__ioinit): Define here instead if
init_priority is usable, via ...
* src/c++98/ios_base_init.h: ... this new file.
Diff:
---
libstdc++-v3/include/std/iostream | 4 ++++
libstdc++-v3/src/c++98/ios_base_init.h | 12 ++++++++++++
libstdc++-v3/src/c++98/ios_init.cc | 2 ++
3 files changed, 18 insertions(+)
diff --git a/libstdc++-v3/include/std/iostream b/libstdc++-v3/include/std/iostream
index 70318a45891..ff78e1cfb87 100644
--- a/libstdc++-v3/include/std/iostream
+++ b/libstdc++-v3/include/std/iostream
@@ -73,7 +73,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
///@}
// For construction of filebuffers for cout, cin, cerr, clog et. al.
+ // When the init_priority attribute is usable, we do this initialization
+ // in the compiled library instead (src/c++98/ios_init.cc).
+#if !__has_attribute(__init_priority__)
static ios_base::Init __ioinit;
+#endif
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
diff --git a/libstdc++-v3/src/c++98/ios_base_init.h b/libstdc++-v3/src/c++98/ios_base_init.h
new file mode 100644
index 00000000000..1c71038f4a1
--- /dev/null
+++ b/libstdc++-v3/src/c++98/ios_base_init.h
@@ -0,0 +1,12 @@
+// This is only in a header so we can use the system_header pragma,
+// to suppress the warning caused by using a reserved init_priority.
+#pragma GCC system_header
+
+// If the target supports init priorities, set up a static object in the
+// compiled library to perform the <iostream> initialization once and
+// sufficiently early (so that it happens before any other global
+// constructor when statically linking with libstdc++.a), instead of
+// doing so in (each TU that includes) <iostream>.
+#if __has_attribute(init_priority)
+static ios_base::Init __ioinit __attribute__((init_priority(90)));
+#endif
diff --git a/libstdc++-v3/src/c++98/ios_init.cc b/libstdc++-v3/src/c++98/ios_init.cc
index 1b5132f1c2d..4016fcab785 100644
--- a/libstdc++-v3/src/c++98/ios_init.cc
+++ b/libstdc++-v3/src/c++98/ios_init.cc
@@ -75,6 +75,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
extern wostream wclog;
#endif
+#include "ios_base_init.h"
+
ios_base::Init::Init()
{
if (__gnu_cxx::__exchange_and_add_dispatch(&_S_refcount, 1) == 0)
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