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Make qglobal.h complain if you use -fPIE

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Prior to Qt 5.4.2 (commit 36d6eb721e), we
allowed it, but now we need to enforce that it is not used. Note that
-fPIE does define __PIC__, so we need this to catch the use of -fPIE.

[ChangeLog][Important Behavior Changes] On x86 and x86-64 systems with
ELF binaries (especially Linux), due to a new optimization in GCC 5.x in
combination with a recent version of GNU binutils, compiling Qt
applications with -fPIE is no longer enough. Applications now need to be
compiled with the -fPIC option if Qt's option "reduce relocations" is
active. Note that Clang is known to generate incompatible code even with
-fPIC if the -flto option is active.

Task-number: QTBUG-45755
Change-Id: I66a35ce5f88941f29aa6ffff13dd210e0aa2728f
Reviewed-by: Dmitry Shachnev <mitya57@gmail.com>
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>
This commit is contained in:
Thiago Macieira 2015-05-11 18:30:00 +09:00 committed by Simon Hausmann
parent 3a726628f1
commit 3eca75de67
2 changed files with 9 additions and 2 deletions
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7
dist/changes-5.4.2 vendored
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@ -34,6 +34,13 @@ information about a particular change.
common EXIF-format (big-endian) was not working until 5.4.1. 5.4.2 restores the
behavior of 5.4.0 and earlier for most EXIF-tagged JPEGs.
EXIF orientation will be an opt-in starting with Qt 5.5.
- On x86 and x86-64 systems with ELF binaries (especially Linux), due to
a new optimization in GCC 5.x in combination with a recent version of
GNU binutils, compiling Qt applications with -fPIE is no longer
enough. Applications now need to be compiled with the -fPIC option if
Qt's option "reduce relocations" is active. Note that Clang is known
to generate incompatible code even with -fPIC if the -flto option is
active.
****************************************************************************
* Library *

4
src/corelib/global/qglobal.h
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@ -1047,9 +1047,9 @@ Q_CORE_EXPORT int qrand();
# define QT_NO_SHAREDMEMORY
#endif
#if !defined(QT_BOOTSTRAPPED) && defined(QT_REDUCE_RELOCATIONS) && defined(__ELF__) && !defined(__PIC__)
#if !defined(QT_BOOTSTRAPPED) && defined(QT_REDUCE_RELOCATIONS) && defined(__ELF__) && (!defined(__PIC__) || defined(__PIE__))
# error "You must build your code with position independent code if Qt was built with -reduce-relocations. "\
"Compile your code with -fPIC."
"Compile your code with -fPIC (-fPIE is not enough)."
#endif
namespace QtPrivate {