we have an application that is mostly Go (1.17) that makes a lot of calls through CGo (GCC 7.5) to CUDA on an ARM processor. We occasionally see panics that look like something has done bad things to the heap in the C side. I tried running the whole application under valgrind, but I get too many messages like
==14869== Thread 1:
==14869== Invalid read of size 8
==14869== at 0x4783AC: runtime.startm (proc.go:2508)
==14869== by 0x47890B: runtime.wakep (proc.go:2584)
==14869== by 0x47CF8F: runtime.newproc.func1 (proc.go:4261)
==14869== by 0x4A476B: runtime.systemstack (asm_arm64.s:230)
==14869== by 0x4A465F: runtime.mstart (asm_arm64.s:117)
==14869== Address 0x1fff0001a8 is on thread 1's stack
==14869== 8 bytes below stack pointer
to see anything useful. I am assuming these are false positives, and the Go runtime is not in fact riddled with undefined behaviour. I can't see a flag to suppress that check. Have I missed it? Is there some other way to investigate this problem? I could write test harnesses in C++ but that will change the use pattern which I suspect is key to the problem.
I build the cgo software to an executable with
go build
which produces an executable by the name of the directory you are in. Let's say it's call "mycgoprog"
I then run valgrind against it with this command:
G_SLICE=always-malloc G_DEBUG=gc-friendly valgrind -v --tool=memcheck --leak-check=full --num-callers=40 --log-file=valgrind.log ./mycgoprog
The valgrind.log then contains the all the indiscretions detected by valgrind in the linked c code.
Related
I've installed GnuCOBOL 2.2 on my Ubuntu 17.04 system. I've written a basic hello world program to test the compiler.
1 IDENTIFICATION DIVISION.
2 PROGRAM-ID. HELLO-WORLD.
3 *---------------------------
4 DATA DIVISION.
5 *---------------------------
6 PROCEDURE DIVISION.
7 DISPLAY 'Hello, world!'.
8 STOP RUN.
This program is entitled HelloWorld.cbl. When I compile the program with the command
cobc HelloWorld.cbl
HelloWorld.so is produced. When I attempt to run the compiled program using
cobcrun HelloWorld
I receive the following error:
libcob: entry point 'HelloWorld' not found
Can anyone explain to me what an entry point is in GnuCOBOL, and perhaps suggest a way to fix the problem and successfully execute this COBOL program?
According to the official manual of GNUCOBOL, you should compile your code with:
cobc -x HelloWorld.cbl
then run it with
./HelloWorld
You can also read GNUCOBOL wiki page which contains some exmaples for further information.
P.S. As Simon Sobisch said, If you change your file name to HELLO-WORLD.cbl to match the program ID, the same commands that you have used will be ok:
cobc HELLO-WORLD.cbl
cobcrun HELLO-WORLD
Can anyone explain to me what an entry point is in GnuCOBOL, and perhaps suggest a way to fix the problem and successfully execute this COBOL program?
An entry point is a point where you may enter a shared object (this is actually more C then COBOL).
GnuCOBOL generates entry points for each PROGRAM-ID, FUNCTION-ID and ENTRY. Therefore your entry point is HELLO-WORLD (which likely gets a conversion as - is no valid identifier in ANSI C - you won't have to think about this when CALLing a program as the conversion will be done internal).
Using cobcrun internally does:
search for a shared object (in your case HelloWord), as this is found (because you've generated it) it will be loaded
search for an entry point in all loaded modules - which isn't found
There are three possible options to get this working:
As mentioned in Ho1's answer: use cobc -x, the reason that this works is because you don't generate a shared object at all but a C main which is called directly (= the entry point doesn't apply at all)
preload the shared object and calling the program by its PROGRAM-ID (entry point), either manually with COB_PRE_LOAD=HelloWorld cobcrun HELLO-WORLD or through cobcrun (option available since GnuCOBOL 2.x) cobcrun -M HelloWorld HELLO-WORLD
change the PROGRAM-ID to match the source name (either rename or change the source, I'd do the second: PROGRAM-ID. HelloWorld.)
I have been following this tutorial for reference:
http://valgrind.org/docs/manual/ms-manual.html
When I am using it to profile my Application Using the command:
valgrind --tool=massif --time-unit=B ./run.o
It finishes but does not produce any output file.
Here is the log while running it using the mentioned command.
https://www.dropbox.com/s/yae78rm9wmdbph1/ValGring_massif_Log?dl=0
Kindly suggest why it won't produce a massif.out.xxxxx file ?
If you look in your log file you will see that Valgrind has
crashed, and it explains why, and what you should do to fix it.
valgrind: m_mallocfree.c:304 (get_bszB_as_is): Assertion 'bszB_lo == bszB_hi' failed.
valgrind: Heap block lo/hi size mismatch: lo = 91849568, hi = 1425748016.
This is probably caused by your program erroneously writing past the
end of a heap block and corrupting heap metadata. If you fix any
invalid writes reported by Memcheck, this assertion failure will
probably go away. Please try that before reporting this as a bug.
Use Valgrind's memcheck to fix
your program and try again.
When I perform the PGO optimization step (using LINK.EXE /LTCG:PGU), the Visual Studio 2010 linker complains:
Merging foo!1.pgc
'FOO_EDGE::get_input': Arc 2 --> 4 has negative count (-414343)
Expectation failed: f line 4241
'FOO_DELAY::set_delay': Block 18 outgoing counts differ from block count (-9 diff)
Expectation failed: f line 4261
Expectation failed: f line 4211
'FOO_DELAY::set_delay': Arc 12 --> 23 has negative count (-3)
Expectation failed: f line 4220
Generating code
907 of 4948 ( 18.33%) profiled functions will be compiled for speed
4948 of 4948 functions (100.0%) were optimized using profile data
42912225037 of 42912225037 instructions (100.0%) were optimized using profile data
What's causing these "expectation failures"? How should I address them? It seems like PGO is still optimizing the code, but I'm a little suspicious of the quality/completeness of the optimizations in the presence of these messages.
It seems that these errors occur when performing PGO-instrumented runs of multithreaded applications. They can be avoided by compiling (not linking) with the /PogoSafeMode flag on x64.
I didn't find the MSDN documentation on this flag particularly clear; the correct procedure for performing PGO on multithreaded code is:
Compile with cl.exe /PogoSafeMode
Link with link.exe /LTCG:PGI
Execute your multithreaded profiling run(s)
Re-link with link.exe /LTCG:PGO
I am trying to use GDB to debug a Linux kernel zImage before it is decompressed. The kernel is running on an ARM target and I have a JTAG debugger connected to it with a GDB server stub. The target has to load a boot loader. The boot loader reads the kernel image from flash and puts it in RAM at 0x20008000, then branches to that location.
I have started GDB and connected to the remote target, then I use GDB's add-symbol-file command like so:
add-symbol-file arch/arm/boot/compressed/vmlinux 0x20008000 -readnow
When I set a breakpoint for that address, it does trap at the correct place - right when it branches to the kernel. However, GDB shows the wrong line from the source of arch/arm/boot/compressed/head.S. It's 4 lines behind. How can I fix this?
I also have tried adding the -s section addr option to add-symbol-file with -s .start 0x20008000; this results in exactly the same problem.
There are assembler macros that print out stuff when compiling with low level debug. You have to make sure the macros are appropriate for your board.
linux-latest/arch/arm$ find . -name debug-macro.S | wc
56 56 2306
Find the file for your board and ensure the correct serial port registers are hit. You can instrument the code with out using JTAG. These macros are used in the decompress code. Of course configure with *CONFIG_DEBUG_LL*.
Most likely the ATAGs are not correct or one of the other requirements. Checkout Documentation/arm/Booting to make sure you have registers set properly. Note there is a new requirement with recent kernels to send a dt list.
I m using gdb on a aix shared lib running on aix 5.3?
When i try to run gdb for this file
i get a error message saying ""Architecture of file not recognized"
Don't know how to get this fixed.
Does anybody know why i get this message ""Architecture of file not recognized"?.
gdb runs fine on other executables compiled by xlc.
Is there some option that i might have used while compiling , which is not compatible with GDB.some processor specific option.
I compiled the shared lib w xlc v9.0 for aix.
Thanks.
You don't run GDB on a shared library, you run it on an executable.
If the executable loads your shared library, GDB will know about it.
void
set_gdbarch_from_file (bfd *abfd)
{
struct gdbarch_info info;
struct gdbarch *gdbarch;
gdbarch_info_init (&info);
info.abfd = abfd;
info.target_desc = target_current_description ();
gdbarch = gdbarch_find_by_info (info);
if (gdbarch == NULL)
error (_("Architecture of file not recognized."));
deprecated_current_gdbarch_select_hack (gdbarch);
}
This is the actual GDB code in question (gdb/arch-utils.c:530-544).
The information passed to the gdbarch pointer seems to be invalid. This is caused by gdb_find_by_info returning a NULL pointer and that is caused by find_arch_by_info (gdb/gdbarch.c:3656) returning a NULL pointer.
It basically means what it says: GDB could not identify the architecture of the file. This seems to be a common problem for xlc, even on recent gdb versions.
XLC and gdb are, as far i remember and understand, not very good when it comes down to compatability terms (AIX support is minimal), you might try using the Gnu C Compiler .You might look at the GDB sources for VERY specific information (that i can't really give you).
Here is a link to gcc-AIX specifics.