<div dir="ltr"><div>A few days ago, I tried to change the optimization flag from -O0 to -O2 to speed up the execution of the application on Ubuntu/ARM 14.04 32 bit. </div><div>When I compiled the source code with -O2 flag instead of -O0 flag, I could not run the application normally by getting always the segmentation fault.</div><div><br></div><div><p style="margin-top:0px;margin-bottom:16px;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,'Segoe UI',Arial,freesans,sans-serif,'Apple Color Emoji','Segoe UI Emoji','Segoe UI Symbol';font-size:14px;line-height:22.4px">Here is debugging information with GDB command in case of that. As you can see, we could not execute simple hello!! console application <br>because of the bug of clang/LLVM when we try to use "static __thread" variable with -O2 flag. </p><pre style="font-family:Consolas,'Liberation Mono',Menlo,Courier,monospace;font-size:11.9px;margin-top:0px;font-stretch:normal;line-height:1.45;padding:16px;overflow:auto;border-radius:3px;word-wrap:normal;color:rgb(51,51,51);margin-bottom:0px!important;background-color:rgb(247,247,247)"><code style="font-family:Consolas,'Liberation Mono',Menlo,Courier,monospace;font-size:11.9px;padding:0px;margin:0px;border-radius:3px;border:0px;display:inline;max-width:initial;overflow:initial;line-height:inherit;word-wrap:normal;background:transparent"><b>root:/dotnet/runtime.release.20160322.2/example> gdb ../corerun ./core.20160322</b>
GNU gdb (GDB) 7.9.1
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License GPLv3+: GNU GPL version 3 or later <<a href="http://gnu.org/licenses/gpl.html">http://gnu.org/licenses/gpl.html</a>>
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Reading symbols from ../corerun...(no debugging symbols found)...done.
[New LWP 742]
[New LWP 745]
[New LWP 744]
[New LWP 743]
[New LWP 746]
warning: File "/lib/arm-linux-gnueabihf/<a href="http://libthread_db-1.0.so">libthread_db-1.0.so</a>" auto-loading has been declined
by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
To enable execution of this file add
add-auto-load-safe-path /lib/arm-linux-gnueabihf/<a href="http://libthread_db-1.0.so">libthread_db-1.0.so</a>
line to your configuration file "//.gdbinit".
To completely disable this security protection add
set auto-load safe-path /
line to your configuration file "//.gdbinit".
For more information about this security protection see the
"Auto-loading safe path" section in the GDB manual. E.g., run from the shell:
info "(gdb)Auto-loading safe path"
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
warning: File "/lib/arm-linux-gnueabihf/<a href="http://libthread_db-1.0.so">libthread_db-1.0.so</a>" auto-loading has been declined
by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
---Type <return> to continue, or q <return> to quit---
Core was generated by `../corerun -c .. ./hello.exe'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x76f7a410 in __tls_get_addr () from /lib/ld-linux-armhf.so.3
(gdb) thread info
No symbol "info" in current context.
(gdb) bt
#0 0x76f7a410 in __tls_get_addr () from /lib/ld-linux-armhf.so.3
#1 0x7699787c in ClassLoader::LoadTypeHandleForTypeKey_Body(TypeKey*, TypeHandle, ClassLoadLevel) () from /dotnet/runtime.release.20160222.2/libcoreclr.so
#2 0x76994c4a in ClassLoader::LoadTypeHandleForTypeKey(TypeKey*, TypeHandle, ClassLoadLevel, InstantiationContext const*) ()
from /dotnet/runtime.release.20160222.2/libcoreclr.so
#3 0x76995a38 in ClassLoader::LoadTypeDefThrowing(Module*, unsigned int, ClassLoader::NotFoundAction, ClassLoader::PermitUninstantiatedFlag, unsigned int, ClassLoadLevel, Instantiation*) ()
from /dotnet/runtime.release.20160222.2/libcoreclr.so
#4 0x769939f2 in ClassLoader::LoadTypeHandleThrowing(NameHandle*, ClassLoadLevel, Module*) () from /dotnet/runtime.release.20160222.2/libcoreclr.so
#5 0x769937c2 in ClassLoader::LoadTypeByNameThrowing(Assembly*, char const*, char const*, ClassLoader::NotFoundAction, ClassLoader::LoadTypesFlag, ClassLoadLevel) () from /dotnet/runtime.release.20160222.2/libcoreclr.so
#6 0x76980918 in MscorlibBinder::LookupClass(BinderClassID) ()
from /dotnet/runtime.release.20160222.2/libcoreclr.so
#7 0x769675ca in SystemDomain::LoadBaseSystemClasses() ()
from /dotnet/runtime.release.20160222.2/libcoreclr.so
#8 0x769673ac in SystemDomain::Init() ()
from /dotnet/runtime.release.20160222.2/libcoreclr.so
#9 0x768dbc16 in EEStartupHelper(tagCOINITEE) ()
from /dotnet/runtime.release.20160222.2/libcoreclr.so
---Type <return> to continue, or q <return> to quit---
#10 0x768db070 in EEStartup(tagCOINITEE) ()
from /dotnet/runtime.release.20160222.2/libcoreclr.so
#11 0x768daf56 in EnsureEEStarted(tagCOINITEE) ()
from /dotnet/runtime.release.20160222.2/libcoreclr.so
#12 0x76857998 in CorHost2::Start() ()
from /dotnet/runtime.release.20160222.2/libcoreclr.so
#13 0x76842eac in coreclr_initialize ()
from /dotnet/runtime.release.20160222.2/libcoreclr.so
#14 0x0000a52e in ExecuteManagedAssembly(char const*, char const*, char const*, int, char const**) ()
#15 0x00009852 in corerun(int, char const**) ()
#16 0x76d38632 in __libc_start_main () from /lib/arm-linux-gnueabihf/libc.so.6
#17 0x00009590 in _start ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb)
(gdb)
(gdb)
(gdb) </code></pre></div><div><br></div><div><br></div><div><div><br class="">At that time, I defined the "global-dynamic" TLS model by default with Clang/LLVM compiler as following: </div><div>SET (CMAKE_C_FLAGS_INIT "-Wall -std=c11 -ftls-model=global-dynamic")<br><br>We can build and run hello!!! console application with clang/LLVM with -O1 optimization level for Ubuntu/ARM 14.04 32bit as following.<br></div><div><span style="color:rgb(0,0,0);white-space:pre-wrap">
src/pal/tools/clang-compiler-override.txt | 13 +++++++++++--</span><br></div><div><pre style="color:rgb(0,0,0);word-wrap:break-word;white-space:pre-wrap"> 1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/src/pal/tools/clang-compiler-override.txt b/src/pal/tools/clang-compiler-override.txt
index 8bba4a9..ba86d15 100644
--- a/src/pal/tools/clang-compiler-override.txt
+++ b/src/pal/tools/clang-compiler-override.txt
@@ -1,13 +1,22 @@
SET (CMAKE_C_FLAGS_INIT "-Wall -std=c11")
SET (CMAKE_C_FLAGS_DEBUG_INIT "-g -O0")
SET (CLR_C_FLAGS_CHECKED_INIT "-g -O2")
-SET (CMAKE_C_FLAGS_RELEASE_INIT "-g -O3")
+if(CMAKE_SYSTEM_NAME STREQUAL Linux AND CMAKE_SYSTEM_PROCESSOR STREQUAL armv7l)
+ SET (CMAKE_C_FLAGS_RELEASE_INIT "-g0 -O1")
+else()
+ SET (CMAKE_C_FLAGS_RELEASE_INIT "-g0 -O3")
+ message(FATAL_ERROR "RELEASE... c flag no-arm")
+endif()
SET (CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-g -O2")
SET (CMAKE_CXX_FLAGS_INIT "-Wall -Wno-null-conversion -std=c++11")
SET (CMAKE_CXX_FLAGS_DEBUG_INIT "-g -O0")
SET (CLR_CXX_FLAGS_CHECKED_INIT "-g -O2")
-SET (CMAKE_CXX_FLAGS_RELEASE_INIT "-g -O3")
+if(CMAKE_SYSTEM_NAME STREQUAL Linux AND CMAKE_SYSTEM_PROCESSOR STREQUAL armv7l)
+ SET (CMAKE_CXX_FLAGS_RELEASE_INIT "-g0 -O1")
+else()
+ SET (CMAKE_CXX_FLAGS_RELEASE_INIT "-g0 -O3")
+endif()
SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-g -O2")
</pre></div><div>In the summary, We can build and run clang/LLVM source code including __thread variable with -O1 /-O2 flags.</div><div><br></div><div>However, We cannot run (build is okay.) normally hello!!! console application with clang/LLVM using -O2 and -O3 optimization level.<br><br></div><div>Anyone who has similar experience that gets the __thread variable issue with -O2/-O3 flags like me? </div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div><a href="http://leemgs.fedorapeople.org" style="font-family:Tahoma" target="_blank">http://leemgs.fedorapeople.org</a><span style="font-family:Tahoma"> </span></div><div>Don't try to avoid pain if you fail.<br>If you decided to face the challenges in life, <br>you can gain a lot by giving your best.<br>Cheolsang Jeong's Book & life<br>--<br></div></div></div>
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