From a57d1aaafe47dadaa5fad8b73ec9e2e31bb5f123 Mon Sep 17 00:00:00 2001

From: Paolo Bonzini <pbonzini@redhat.com>

Date: Thu, 8 Oct 2020 15:30:24 +0200

Subject: [PATCH] build: use PIE objects for static libraries if

 b_staticpic=false but b_pie=true

If static_library is used as a convenience library (e.g. for link_whole)

it should in principle not need position independent code.

However, if the executables that the libraries is linked to are PIE,

the non-PIC objects in the static library will cause linker errors.

To avoid this, obey b_pie for static libraries if either b_staticpic=false

or they use "pic: false".

Without this patch, QEMU cannot use b_staticpic, which causes a slowdown

on some QEMU benchmarks up to 20%.

(cherry picked from commit 021d242f9ce8e6cd804af0c1eb4179b8c83fd470)

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 mesonbuild/backend/backends.py |  2 +-

 mesonbuild/build.py            | 18 +++++++++++-------

 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py

index c84bb7534..f67efe370 100644

--- a/mesonbuild/backend/backends.py

+++ b/mesonbuild/backend/backends.py

@@ -694,7 +694,7 @@ class Backend:

         # Set -fPIC for static libraries by default unless explicitly disabled

         if isinstance(target, build.StaticLibrary) and target.pic:

             commands += compiler.get_pic_args()

-        if isinstance(target, build.Executable) and target.pie:

+        elif isinstance(target, (build.StaticLibrary, build.Executable)) and target.pie:

             commands += compiler.get_pie_args()

         # Add compile args needed to find external dependencies. Link args are

         # added while generating the link command.

diff --git a/mesonbuild/build.py b/mesonbuild/build.py

index a06979cea..90cbd1aa6 100644

--- a/mesonbuild/build.py

+++ b/mesonbuild/build.py

@@ -972,13 +972,13 @@ This will become a hard error in a future Meson release.''')

             if m.is_darwin() or m.is_windows():

                 self.pic = True

             else:

-                self.pic = self._extract_pic_pie(kwargs, 'pic')

-        if isinstance(self, Executable):

+                self.pic = self._extract_pic_pie(kwargs, 'pic', environment, 'b_staticpic')

+        if isinstance(self, Executable) or (isinstance(self, StaticLibrary) and not self.pic):

             # Executables must be PIE on Android

             if self.environment.machines[self.for_machine].is_android():

                 self.pie = True

             else:

-                self.pie = self._extract_pic_pie(kwargs, 'pie')

+                self.pie = self._extract_pic_pie(kwargs, 'pie', environment, 'b_pie')

         self.implicit_include_directories = kwargs.get('implicit_include_directories', True)

         if not isinstance(self.implicit_include_directories, bool):

             raise InvalidArguments('Implicit_include_directories must be a boolean.')

@@ -990,14 +990,20 @@ This will become a hard error in a future Meson release.''')

             if self.gnu_symbol_visibility not in permitted:

                 raise InvalidArguments('GNU symbol visibility arg {} not one of: {}'.format(self.symbol_visibility, ', '.join(permitted)))

-    def _extract_pic_pie(self, kwargs, arg):

+    def _extract_pic_pie(self, kwargs, arg, environment, option):

         # Check if we have -fPIC, -fpic, -fPIE, or -fpie in cflags

         all_flags = self.extra_args['c'] + self.extra_args['cpp']

         if '-f' + arg.lower() in all_flags or '-f' + arg.upper() in all_flags:

             mlog.warning("Use the '{}' kwarg instead of passing '{}' manually to {!r}".format(arg, '-f' + arg, self.name))

             return True

-        val = kwargs.get(arg, False)

+        if arg in kwargs:

+            val = kwargs[arg]

+        elif option in environment.coredata.base_options:

+            val = environment.coredata.base_options[option].value

+        else:

+            val = False

+

         if not isinstance(val, bool):

             raise InvalidArguments('Argument {} to {!r} must be boolean'.format(arg, self.name))

         return val

@@ -1611,8 +1617,6 @@ class StaticLibrary(BuildTarget):

     def __init__(self, name, subdir, subproject, for_machine: MachineChoice, sources, objects, environment, kwargs):

         self.typename = 'static library'

-        if 'pic' not in kwargs and 'b_staticpic' in environment.coredata.base_options:

-            kwargs['pic'] = environment.coredata.base_options['b_staticpic'].value

         super().__init__(name, subdir, subproject, for_machine, sources, objects, environment, kwargs)

         if 'cs' in self.compilers:

             raise InvalidArguments('Static libraries not supported for C#.')

-- 

2.27.0