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gprof producing no output for a program that takes reasonable time to execute

I know that similar questions have been asked before, but:

  1. In regards to gprof produces empty output I am using GCC 10.2.0 from MSYS2 on Windows 10, i.e. it's a MingW64 distribution. I have also added -no-pie to the linker arguments with no results still. The version of GNU Prof is 2.36.1
  2. In regards to gprof gives no output I am executing this on a program that explicitly takes time to execute.

The program is the code from this tutorial which is replicated below:

//test_gprof.c
#include<stdio.h>

void new_func1(void)
{
    printf("\n Inside new_func1()\n");
    int i = 0;

    for(;i<0xffffffee;i++);

    return;
}

void func1(void)
{
    printf("\n Inside func1 \n");
    int i = 0;

    for(;i<0xffffffff;i++);
    new_func1();

    return;
}

static void func2(void)
{
    printf("\n Inside func2 \n");
    int i = 0;

    for(;i<0xffffffaa;i++);
    return;
}

int main(void)
{
    printf("\n Inside main()\n");
    int i = 0;

    for(;i<0xffffff;i++);
    func1();
    func2();

    return 0;
}

I'm building with Code::Blocks. I've tried with both the 32bit and 64bit versions of MingW from MSYS2. I've upgraded everything to the latest versions of the packages available.

Output from the Code::Blocks build log:

g++.exe -pg -c C:\Users\david\Documents\GameDev\CPPTESTS\main.cpp -o obj\Debug\CPPTESTS\main.o
g++.exe -o CPPTESTS-d.exe obj\Debug\CPPTESTS\main.o -pg -lgmon -no-pie

The program compiles and executes successfully. After execution, a gmon.out file is generated. Executing gprof to interpret this file:

 gprof CPPTests-d.exe gmon.out > gprofoutput.txt

produces the following in gprofoutput.txt:

Flat profile:

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total           
 time   seconds   seconds    calls  Ts/call  Ts/call  name    

 %         the percentage of the total running time of the
time       program used by this function.

cumulative a running sum of the number of seconds accounted
 seconds   for by this function and those listed above it.

 self      the number of seconds accounted for by this
seconds    function alone.  This is the major sort for this
           listing.

calls      the number of times this function was invoked, if
           this function is profiled, else blank.

 self      the average number of milliseconds spent in this
ms/call    function per call, if this function is profiled,
       else blank.

 total     the average number of milliseconds spent in this
ms/call    function and its descendents per call, if this
       function is profiled, else blank.

name       the name of the function.  This is the minor sort
           for this listing. The index shows the location of
       the function in the gprof listing. If the index is
       in parenthesis it shows where it would appear in
       the gprof listing if it were to be printed.

Copyright (C) 2012-2021 Free Software Foundation, Inc.

Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.

             Call graph (explanation follows)


granularity: each sample hit covers 4 byte(s) no time propagated

index % time    self  children    called     name

 This table describes the call tree of the program, and was sorted by
 the total amount of time spent in each function and its children.

 Each entry in this table consists of several lines.  The line with the
 index number at the left hand margin lists the current function.
 The lines above it list the functions that called this function,
 and the lines below it list the functions this one called.
 This line lists:
     index  A unique number given to each element of the table.
        Index numbers are sorted numerically.
        The index number is printed next to every function name so
        it is easier to look up where the function is in the table.

     % time This is the percentage of the `total' time that was spent
        in this function and its children.  Note that due to
        different viewpoints, functions excluded by options, etc,
        these numbers will NOT add up to 100%.

     self   This is the total amount of time spent in this function.

     children   This is the total amount of time propagated into this
        function by its children.

     called This is the number of times the function was called.
        If the function called itself recursively, the number
        only includes non-recursive calls, and is followed by
        a `+' and the number of recursive calls.

     name   The name of the current function.  The index number is
        printed after it.  If the function is a member of a
        cycle, the cycle number is printed between the
        function's name and the index number.


 For the function's parents, the fields have the following meanings:

     self   This is the amount of time that was propagated directly
        from the function into this parent.

     children   This is the amount of time that was propagated from
        the function's children into this parent.

     called This is the number of times this parent called the
        function `/' the total number of times the function
        was called.  Recursive calls to the function are not
        included in the number after the `/'.

     name   This is the name of the parent.  The parent's index
        number is printed after it.  If the parent is a
        member of a cycle, the cycle number is printed between
        the name and the index number.

 If the parents of the function cannot be determined, the word
 `<spontaneous>' is printed in the `name' field, and all the other
 fields are blank.

 For the function's children, the fields have the following meanings:

     self   This is the amount of time that was propagated directly
        from the child into the function.

     children   This is the amount of time that was propagated from the
        child's children to the function.

     called This is the number of times the function called
        this child `/' the total number of times the child
        was called.  Recursive calls by the child are not
        listed in the number after the `/'.

     name   This is the name of the child.  The child's index
        number is printed after it.  If the child is a
        member of a cycle, the cycle number is printed
        between the name and the index number.

 If there are any cycles (circles) in the call graph, there is an
 entry for the cycle-as-a-whole.  This entry shows who called the
 cycle (as parents) and the members of the cycle (as children.)
 The `+' recursive calls entry shows the number of function calls that
 were internal to the cycle, and the calls entry for each member shows,
 for that member, how many times it was called from other members of
 the cycle.

Copyright (C) 2012-2021 Free Software Foundation, Inc.

Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.

Index by function name

which you can see it's completely empty. Further, if I open gmon.out in a hex editor, it's mostly blank inside, here's the first bit:

F0 14 C5 00 18 8A C5 00 B4 3A 00 00 79 18 05 00 64 00 00 00 96 1A C5 00 A7 16 C5 00 20 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 05 00 FE 00 5D 00 E2 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 07 00 C6 01 A5 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 06 00 E5 00 77 00 F5 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

and then the end is the following:

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 E4 15 C5 00 6C 89 C5 00 01 00 00 00 14 16 C5 00 6C 89 C5 00 01 00 00 00 2C 16 C5 00 DB 15 C5 00 01 00 00 00 48 16 C5 00 6C 89 C5 00 01 00 00 00 84 16 C5 00 6C 89 C5 00 01 00 00 00 A0 16 C5 00 0A 16 C5 00 01 00 00 00 A4 16 C5 00 3C 16 C5 00 01 00 00 00

The rest is a few kilobytes of 00.

I have tried everything I can find in google about getting this to work. Originally I was having trouble executing it on actual code for a project, but have resorted to using the code above as there seems to be something I'm doing wrong which I just can't figure out.

Any help would be appreciated.

EDIT

I managed to produce results in gmon.out that were parsed correctly with gprof and gave me timing for all the functions in my test program. Making no changes, not even closing the MSYS2 terminal (I abandoned Code::Blocks to be sure it wasn't the issue) , I then recompiled the program with the same command, executed it again, and back to having an empty results.

It's unclear to me if it's something during compilation (hard to believe, it was compiled using the last command in the terminal history), or something on my machine when I execute it. Or if it's a problem with gprof translating the gmon.out file.

EDIT 2

I've executed the program on a different machine (it's a similar Windows 10 Surface Pro) that has never been used for development. It's produced gmon.out also seems to have no results when parsed through gprof.

EDIT 3

I've tired with both gcc and g++ with the same results. I've tried separate compilation and link steps or doing both together. I've tried linking to -lgmon or not as well. All gives same empty results when gprof is parsed.

I haven't been able to get results again since the one random time that it worked.

EDIT 4

I compiled the program with both -g and -pg and then ran it through VTune. I can see within a Hotspots analysis that function calls related to the profiler are being called.

Here's the entire callee stack. You can see the profile-related function calls profthr_func and get_thrpc being called.

Callees CPU Time: Total CPU Time: Self
BaseThreadInitThunk 100.0%  0s
  _tmainCRTStartup  99.1%   0s
    main    99.1%   0.016s
      func1 65.8%   20.521s
        new_func1   32.8%   20.456s
      func2 33.2%   20.695s
  profthr_func  0.6%    0.009s
    WaitForSingleObject 0.4%    0.231s
    get_thrpc   0.2%    0s
      SwitchToThread    0.2%    0.116s
      TlsGetValue   0.0%    0.002s
      GetLastError  0.0%    0.001s
      SwitchToThread    0.0%    0.001s
      GetLastError  0.0%    0.001s
      [Outside any known module]    0.0%    0.001s
      func@0x4b308730   0.0%    0.000s
      TlsGetValue   0.0%    0.000s
  get_thrpc 0.4%    0s
    GetThreadContext    0.3%    0.214s
    GetLastError    0.0%    0.006s
    TlsGetValue 0.0%    0.000s
  [Outside any known module]    0.0%    0.002s
  SuspendThread 0.0%    0.001s
  [Unknown stack frame(s)]  0.0%    0s
    profthr_func    0.0%    0s
      WaitForSingleObject   0.0%    0.000s

And then all the functions and their sources etc:

Function                    CPU Time: Total CPU Time: Self  Module          Function (Full)             Source File Start Address
BaseThreadInitThunk         100.0%          0s              kernel32.dll    BaseThreadInitThunk         [Unknown]   0x6b81fa10
func@0x4b2e7a03             100.0%          0s              ntdll.dll       func@0x4b2e7a03             [Unknown]   0x4b2e7a03
func@0x4b2e7a1f             100.0%          0s              ntdll.dll       func@0x4b2e7a1f             [Unknown]   0x4b2e7a1f
_tmainCRTStartup            99.1%           0s              CPPTESTS-d.exe  _tmainCRTStartup            crtexe.c    0x401170
main                        99.1%           0.016s          CPPTESTS-d.exe  main                        main.cpp    0x40165c
func1                       65.8%           20.521s         CPPTESTS-d.exe  func1(void)                 main.cpp    0x4015fd
func2                       33.2%           20.695s         CPPTESTS-d.exe  func2                       main.cpp    0x40162f
new_func1                   32.8%           20.456s         CPPTESTS-d.exe  new_func1(void)             main.cpp    0x4015d0
profthr_func                0.6%            0.009s          CPPTESTS-d.exe  profthr_func                profil.c    0x408620
get_thrpc                   0.5%            0s              CPPTESTS-d.exe  get_thrpc                   profil.c    0x4085c0
WaitForSingleObject         0.4%            0.231s          KernelBase.dll  WaitForSingleObject         [Unknown]   0x10110440
GetThreadContext            0.3%            0.214s          KernelBase.dll  GetThreadContext            [Unknown]   0x101b61a0
SwitchToThread              0.2%            0.116s          KernelBase.dll  SwitchToThread              [Unknown]   0x100f5b40
GetLastError                0.0%            0.007s          kernel32.dll    GetLastError                [Unknown]   0x6b81e010
[Outside any known module]  0.0%            0.002s          [Unknown]       [Outside any known module]  [Unknown]   0
TlsGetValue                 0.0%            0.002s          KernelBase.dll  TlsGetValue                 [Unknown]   0x101193a0
SuspendThread               0.0%            0.001s          kernel32.dll    SuspendThread               [Unknown]   0x6b834e90
SwitchToThread              0.0%            0.001s          kernel32.dll    SwitchToThread              [Unknown]   0x6b817cc0
GetLastError                0.0%            0.001s          KernelBase.dll  GetLastError                [Unknown]   0x10110580
TlsGetValue                 0.0%            0.000s          kernel32.dll    TlsGetValue                 [Unknown]   0x6b81df20
func@0x4b308730             0.0%            0.000s          ntdll.dll       func@0x4b308730             [Unknown]   0x4b308730
[Unknown stack frame(s)]    0.0%            0s              [Unknown]       [Unknown stack frame(s)]    [Unknown]   0

I'm not sure if this information is of any help in sorting out my problem. The gmon.out file once again, when parsed through gprof, features no information.

I've read this answer to a question about how gprof works, so I would expect that the calls to main, func1, func2, and new_func1 would have featured some kind of instrument call?

I ran VTune and checked the Threading option and noticed that gprof seems to do it's thing via a new thread, which is different to my understanding above. However, it doesn't explain why I did once get some output and have no been able to recreate it.

But, in Vtune, I see no calls to mcount which I thought was how gprof worked. It does show me bits and pieces (as you can see in the call stack and function list above) that profiling stuff from the -pg flag is present.

EDIT 5

I've uploaded my compiled program and it's gmon.out in case it helps anyone help answer the question.

EDIT 6

I reinstalled MSYS2 in the hopes that that would solve the problem. It didn't.

EDIT 7

I have tried linking with -static -static-libgcc -static-libstdc++. It had no effect.

EDIT 8

I've executed gprof with -d flag. Debug output can be found here. But it's mostly just gibberish to me.

EDIT 9

I've installed Mingw-Builds directly outside of MSYS2 and tested version 8.1.0, both Dwarf and SJLJ in both i686 and 86_64 versions. After compiling and linking with this version of G++, a gmon.out file is generated, but gprof then gives the following error (or are variation of the number):

BFD: Dwarf Error: Could not find abbrev number 108.

But the generated output works. I've also checked that an 8.1.0 compiled programs gmon.out can be parsed by the newer MSYS2 gprof without issue. So it appears the problem is with more recent versions of Mingw64.

Gprof reports version 2.30, G++ reports version 8.1.0.

EDIT 10

I've tried compiling and running gprof on a clean Windows 7 Virtual Box machine and get the same results. So I don't it's my OS (Windows 10) or my particular computer.

Doesn't look like this question is getting answered here. If I ever figure it out I will answer the question. Until then, I've created issues on both the MSYS2 tracker and Mingw64 tracker.

EDIT 11

I've been working now on the following code:

#include <iostream>

bool is_prime(const int& number)
{
    if(number == 0 || number == 1)
        return false;
    else
    {
        for(int i = 2; i <= number / 2; ++i)
        {
            if(number % i == 0)
            {
                return false;
            }
        }
    }

    return true;
}

int main()
{
    int low = 0;
    int high = 300000;

    while(low < high)
    {
        if(is_prime(low))
            std::cout << low << ", ";

        ++low;
    }

    std::cout << std::endl;
    return 0;
}

using the same compiler flags as previously g++ -g -pg -O0 main.cpp -o CPPTESTS-d.exe

objdump -d CPPTESTS-d.exe provides me with the following from the main and is_prime sections:

004015d0 <__Z8is_primeRKi>:
  4015d0:   55                      push   %ebp
  4015d1:   89 e5                   mov    %esp,%ebp
  4015d3:   83 ec 10                sub    $0x10,%esp
  4015d6:   e8 a5 15 00 00          call   402b80 <_mcount>
  4015db:   8b 45 08                mov    0x8(%ebp),%eax
  4015de:   8b 00                   mov    (%eax),%eax
  4015e0:   85 c0                   test   %eax,%eax
  4015e2:   74 0a                   je     4015ee <__Z8is_primeRKi+0x1e>
  4015e4:   8b 45 08                mov    0x8(%ebp),%eax
  4015e7:   8b 00                   mov    (%eax),%eax
  4015e9:   83 f8 01                cmp    $0x1,%eax
  4015ec:   75 07                   jne    4015f5 <__Z8is_primeRKi+0x25>
  4015ee:   b8 00 00 00 00          mov    $0x0,%eax
  4015f3:   eb 3b                   jmp    401630 <__Z8is_primeRKi+0x60>
  4015f5:   c7 45 fc 02 00 00 00    movl   $0x2,-0x4(%ebp)
  4015fc:   8b 45 08                mov    0x8(%ebp),%eax
  4015ff:   8b 00                   mov    (%eax),%eax
  401601:   89 c2                   mov    %eax,%edx
  401603:   c1 ea 1f                shr    $0x1f,%edx
  401606:   01 d0                   add    %edx,%eax
  401608:   d1 f8                   sar    %eax
  40160a:   39 45 fc                cmp    %eax,-0x4(%ebp)
  40160d:   7f 1c                   jg     40162b <__Z8is_primeRKi+0x5b>
  40160f:   8b 45 08                mov    0x8(%ebp),%eax
  401612:   8b 00                   mov    (%eax),%eax
  401614:   99                      cltd   
  401615:   f7 7d fc                idivl  -0x4(%ebp)
  401618:   89 d0                   mov    %edx,%eax
  40161a:   85 c0                   test   %eax,%eax
  40161c:   75 07                   jne    401625 <__Z8is_primeRKi+0x55>
  40161e:   b8 00 00 00 00          mov    $0x0,%eax
  401623:   eb 0b                   jmp    401630 <__Z8is_primeRKi+0x60>
  401625:   83 45 fc 01             addl   $0x1,-0x4(%ebp)
  401629:   eb d1                   jmp    4015fc <__Z8is_primeRKi+0x2c>
  40162b:   b8 01 00 00 00          mov    $0x1,%eax
  401630:   c9                      leave  
  401631:   c3                      ret    

00401632 <_main>:
  401632:   8d 4c 24 04             lea    0x4(%esp),%ecx
  401636:   83 e4 f0                and    $0xfffffff0,%esp
  401639:   ff 71 fc                push   -0x4(%ecx)
  40163c:   55                      push   %ebp
  40163d:   89 e5                   mov    %esp,%ebp
  40163f:   51                      push   %ecx
  401640:   83 ec 24                sub    $0x24,%esp
  401643:   e8 38 15 00 00          call   402b80 <_mcount>
  401648:   e8 73 1a 00 00          call   4030c0 <__monstartup>
  40164d:   e8 be 01 00 00          call   401810 <___main>
  401652:   c7 45 f0 00 00 00 00    movl   $0x0,-0x10(%ebp)
  401659:   c7 45 f4 e0 93 04 00    movl   $0x493e0,-0xc(%ebp)
  401660:   8b 45 f0                mov    -0x10(%ebp),%eax
  401663:   39 45 f4                cmp    %eax,-0xc(%ebp)
  401666:   7e 3d                   jle    4016a5 <__fu0___ZSt4cout+0x27>
  401668:   8d 45 f0                lea    -0x10(%ebp),%eax
  40166b:   89 04 24                mov    %eax,(%esp)
  40166e:   e8 5d ff ff ff          call   4015d0 <__Z8is_primeRKi>
  401673:   84 c0                   test   %al,%al
  401675:   74 23                   je     40169a <__fu0___ZSt4cout+0x1c>
  401677:   8b 45 f0                mov    -0x10(%ebp),%eax
  40167a:   89 04 24                mov    %eax,(%esp)
  40167d:   b9                      .byte 0xb9

I can see that mcount is called at the start of both. So it appears that the compiled code is instrumented properly, but there's still no output in gprof.

like image 423
NeomerArcana Avatar asked Apr 24 '21 08:04

NeomerArcana


1 Answers

This seems to be a bug in the new version of MinGW. I also encountered the same problem before. My MinGW was downloaded from winlibs. When I tried to use the latest version 9.0, the output result of gprof was indeed empty. I tried MinGW version 9.0 and GCC version 11, 10 and 9, and there would be empty results. Finally, I found mingw7.0.0-gcc10.2, and tried to compile with this version, run and then use gprof, the output result is not empty, but its result is a little strange compared with using gprof on Linux platform

like image 136
kalakuer Avatar answered Nov 15 '22 08:11

kalakuer