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Difference between revisions of "Logo contest"

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((I succeeded my wife))
Tag: Replaced
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* a label, probably "Free Content"
 
* a label, probably "Free Content"
  
Logos '''must''' have a vector graphics source (SVG preferred), but '''must''' be uploaded in any format (PNG preferred). A good, free software vector graphics application which can handle SVG and PNG exports is [http://www.inkscape.org/ inkscape]. The dimensions are up to you as long as the images scale well. In order for your logo to be used, the logo itself must be free content with a reduced attribution requirement, but we can work this out with you once we have picked your logo.
+
Logos '''must''' have a vector graphics source (SVG preferred), but '''must''' be uploaded in any format (PNG preferred). A good, free software vector graphics application which can handle SVG and PNG exports is [http://www.inkscape.org/ inkscape]. The dimensions are up to you as long as the images scale well. In order for your logo to be used, the logo itself must be free content with a reduced attribution requirement, but we can work this out with you once we have picked your Debugging Inkscape
 +
To get debug symbols for Inkscape, you'll probably need to recompile it. We use cmake and it has a Debug mode which produces debugging symbols:
 +
 
 +
cmake -DCMAKE_BUILD_TYPE=Debug ../
 +
This assumes that you're building everything in a build folder and the repository root is the parent directory.
 +
 
 +
If you're looking an older non-cmake version, you'll need to enable the CXXFLAGS manually.
 +
 
 +
Debugging with GDB
 +
To start debugging Inkscape with GDB, load it up:
 +
 
 +
gdb path/to/inkscape
 +
If you want Inkscape to start right away and your version of GDB is new enough, you can start it with
 +
 
 +
gdb path/to/inkscape -ex r
 +
To keep gdb from paginating (splitting output from commands into pages, makes creating backtraces for bug reports more difficult) you can put this in ~/.gdbinit:
 +
 
 +
set pagination off
 +
To use GDB's text UI, you can run gdb -tui or gdbtui.
 +
 
 +
When the program crashes you might see something like this:
 +
 
 +
Program received signal SIGSEGV, Segmentation fault.
 +
0x0000000000000000 in ??
 +
(gdb)
 +
To find out where the crash occurred (you might not always be able to), you should run:
 +
 
 +
(gdb) backtrace
 +
or
 +
 
 +
(gdb) where
 +
or
 +
 
 +
(gdb) bt
 +
Each does the same thing, and refers to the command backtrace.
 +
 
 +
More advanced debugging with GDB
 +
When you run bt, you get a list of frames:
 +
 
 +
Program receieved signal SIGTRAP, Trace/breakpoint trap.
 +
0x0000000000aa849f in SPDesktopWidget::createInstance (namedview=0x33a57a0) at ../../src/widgets/desktop-widget.cpp:1708
 +
1708    UXManager::getInstance()->connectToDesktop( toolboxes, dtw->desktop );
 +
(gdb) bt
 +
#0 0x0000000000aa849f in SPDesktopWidget::createInstance (namedview=0x33a57a0) at ../../src/widgets/desktop-widget.cpp:1708
 +
#1 0x0000000000aa8065 in sp_desktop_widget_new (namedview=0x33a57a0) at ../../src/widgets/desktop-widget.cpp:1659
 +
#2 0x000000000052430d in sp_file_new (templ=...) at ../../src/file.cpp:155
 +
#3 0x00000000005249ba in sp_file_new_default () at ../../src/file.cpp:226
 +
#4 0x000000000048865e in sp_main_gui (argc=1, argv=0x7fffffffe0b8) at ../../src/main.cpp:1071
 +
#5 0x0000000000487fab in main (argc=1, argv=0x7fffffffe0b8) at ../../src/main.cpp:789
 +
(gdb)
 +
These frames are all selectable:
 +
 
 +
(gdb) frame 2
 +
#2 0x000000000052430d in sp_file_new (templ=...) at ../../src/file.cpp:155
 +
(If you have the same crash in a debugger better suited to your platform, you can use select frame to specify the address if GDB cannot find it.)
 +
 
 +
Now you have activated frame 2. You can see the state of the processor registers in frame 2 and any local variables that the compiler has embedded in the debug symbols.
 +
 
 +
(gdb) info locals
 +
doc = 0x27fbea0
 +
myRoot = 0x27f8850
 +
nodeToRemove = 0x0
 +
olddesktop = 0x0
 +
dtw = 0x7fffffffdd30
 +
desktop = 0x33a0710
 +
 
 +
(gdb) print templ
 +
$1 = (const std::string &) @0x7fffffffddb8: {static npos = 18446744073709551615, _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, _M_p = 0x339fdd8 "/usr/local/share/inkscape/templates/default.svg"}}
 +
Stepping execution and breakpoints
 +
Sometimes, you would like to be in control of program execution instead of just letting it run wildly.
 +
 
 +
You can tell GDB to stop when it reaches a certain function, upon a certain condition, or when a value in memory changes. These are known as breakpoints and watchpoints.
 +
 
 +
Stopping when a function is called:
 +
 
 +
(gdb) break Inkscape::UI::Tools::SelectTool::root_handler
 +
Breakpoint 1 at 0xf64ab7: file ../../src/ui/tools/select-tool.cpp, line 460.
 +
Stopping if any exception is thrown:
 +
 
 +
(gdb) catch throw
 +
Catchpoint 2 (throw)
 +
Stopping if a condition is met:
 +
 
 +
(gdb) break ../../src/ui/tools/select-tool.cpp:629 if group_at_point == 0
 +
Breakpoint 3 at 0xf657a5: file ../../src/ui/tools/select-tool.cpp, line 629.
 +
Stopping when a memory value changes:
 +
 
 +
(gdb) print desktop
 +
$2 = (SPDesktop *) 0x33a0710
 +
(gdb) awatch *0x33a0710
 +
Hardware access (read/write) watchpoint 4: *0x33a0710
 +
Listing breakpoints:
 +
 
 +
(gdb) info break
 +
Num    Type          Disp Enb Address            What
 +
1      breakpoint    keep y  0x0000000000f64ab7 in Inkscape::UI::Tools::SelectTool::root_handler(_GdkEvent*) at ../../src/ui/tools/select-tool.cpp:460
 +
2      breakpoint    keep y  0x00007ffff03a4a30 exception throw
 +
3      breakpoint    keep y  0x0000000000f657a5 in Inkscape::UI::Tools::SelectTool::root_handler(_GdkEvent*) at ../../src/ui/tools/select-tool.cpp:629
 +
        stop only if group_at_point == 0
 +
4      acc watchpoint keep y                      *0x33a0710
 +
Disabling breakpoints:
 +
 
 +
(gdb) disable 4
 +
Deleting breakpoints:
 +
 
 +
(gdb) delete 3
 +
Creating breakpoints that will only be stopped on once:
 +
 
 +
(gdb) tbreak foo::bar
 +
(gdb) tcatch throw
 +
Evaluating expressions
 +
If GDB can figure out what you are talking about, it can print pretty much anything. GDB also is immune to the private boundary of a class.
 +
 
 +
(gdb) print arc_context->arc
 +
$3 = (SPGenericEllipse *) 0x3afb610
 +
A handy feature to try to determine if a heap object still exists (hasn't been delete()d yet) is to use the new GDB command info vtbl:
 +
 
 +
(gdb) print UXManager::getInstance()
 +
$4 = (Inkscape::UI::UXManager *) 0x3b6f1d0
 +
(gdb) info vtbl $4
 +
vtable for 'Inkscape::UI::UXManager' @ 0x136e500 (subobject @ 0x3b6f1d0):
 +
[0]: 0xbc7720 <Inkscape::UI::UXManagerImpl::~UXManagerImpl()>
 +
[1]: 0xbc7740 <Inkscape::UI::UXManagerImpl::~UXManagerImpl()>
 +
[2]: 0xbc81e0 <Inkscape::UI::UXManagerImpl::addTrack(SPDesktopWidget*)>
 +
 +
Here's what a delete()d object's vtable might look like:
 +
 
 +
(gdb) call 'operator delete'($4)
 +
(gdb) info vtbl $4
 +
vtable for 'Inkscape::UI::UXManager' @ 0x3f27f80 (subobject @ 0x3b6f1d0):
 +
[0]: 0x190
 +
[1]: 0x20
 +
[2]: 0x3d91db0
 +
[3]: 0x0
 +
[4]: 0x448d40 <g_free@plt>
 +

Revision as of 22:46, 18 May 2021

We need a "Free Content" logo that can be attached to works covered by licenses which meet the conditions defined in the Free Content Definition. This logo should consist of:

  • a symbol or sign that is the same for both logos (minor variations allowed)
  • a label, probably "Free Content"

Logos must have a vector graphics source (SVG preferred), but must be uploaded in any format (PNG preferred). A good, free software vector graphics application which can handle SVG and PNG exports is inkscape. The dimensions are up to you as long as the images scale well. In order for your logo to be used, the logo itself must be free content with a reduced attribution requirement, but we can work this out with you once we have picked your Debugging Inkscape To get debug symbols for Inkscape, you'll probably need to recompile it. We use cmake and it has a Debug mode which produces debugging symbols:

cmake -DCMAKE_BUILD_TYPE=Debug ../ This assumes that you're building everything in a build folder and the repository root is the parent directory.

If you're looking an older non-cmake version, you'll need to enable the CXXFLAGS manually.

Debugging with GDB To start debugging Inkscape with GDB, load it up:

gdb path/to/inkscape If you want Inkscape to start right away and your version of GDB is new enough, you can start it with

gdb path/to/inkscape -ex r To keep gdb from paginating (splitting output from commands into pages, makes creating backtraces for bug reports more difficult) you can put this in ~/.gdbinit:

set pagination off To use GDB's text UI, you can run gdb -tui or gdbtui.

When the program crashes you might see something like this:

Program received signal SIGSEGV, Segmentation fault. 0x0000000000000000 in ?? (gdb) To find out where the crash occurred (you might not always be able to), you should run:

(gdb) backtrace or

(gdb) where or

(gdb) bt Each does the same thing, and refers to the command backtrace.

More advanced debugging with GDB When you run bt, you get a list of frames:

Program receieved signal SIGTRAP, Trace/breakpoint trap. 0x0000000000aa849f in SPDesktopWidget::createInstance (namedview=0x33a57a0) at ../../src/widgets/desktop-widget.cpp:1708 1708 UXManager::getInstance()->connectToDesktop( toolboxes, dtw->desktop ); (gdb) bt

  1. 0 0x0000000000aa849f in SPDesktopWidget::createInstance (namedview=0x33a57a0) at ../../src/widgets/desktop-widget.cpp:1708
  2. 1 0x0000000000aa8065 in sp_desktop_widget_new (namedview=0x33a57a0) at ../../src/widgets/desktop-widget.cpp:1659
  3. 2 0x000000000052430d in sp_file_new (templ=...) at ../../src/file.cpp:155
  4. 3 0x00000000005249ba in sp_file_new_default () at ../../src/file.cpp:226
  5. 4 0x000000000048865e in sp_main_gui (argc=1, argv=0x7fffffffe0b8) at ../../src/main.cpp:1071
  6. 5 0x0000000000487fab in main (argc=1, argv=0x7fffffffe0b8) at ../../src/main.cpp:789

(gdb) These frames are all selectable:

(gdb) frame 2

  1. 2 0x000000000052430d in sp_file_new (templ=...) at ../../src/file.cpp:155

(If you have the same crash in a debugger better suited to your platform, you can use select frame to specify the address if GDB cannot find it.)

Now you have activated frame 2. You can see the state of the processor registers in frame 2 and any local variables that the compiler has embedded in the debug symbols.

(gdb) info locals doc = 0x27fbea0 myRoot = 0x27f8850 nodeToRemove = 0x0 olddesktop = 0x0 dtw = 0x7fffffffdd30 desktop = 0x33a0710

(gdb) print templ $1 = (const std::string &) @0x7fffffffddb8: {static npos = 18446744073709551615, _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, _M_p = 0x339fdd8 "/usr/local/share/inkscape/templates/default.svg"}} Stepping execution and breakpoints Sometimes, you would like to be in control of program execution instead of just letting it run wildly.

You can tell GDB to stop when it reaches a certain function, upon a certain condition, or when a value in memory changes. These are known as breakpoints and watchpoints.

Stopping when a function is called:

(gdb) break Inkscape::UI::Tools::SelectTool::root_handler Breakpoint 1 at 0xf64ab7: file ../../src/ui/tools/select-tool.cpp, line 460. Stopping if any exception is thrown:

(gdb) catch throw Catchpoint 2 (throw) Stopping if a condition is met:

(gdb) break ../../src/ui/tools/select-tool.cpp:629 if group_at_point == 0 Breakpoint 3 at 0xf657a5: file ../../src/ui/tools/select-tool.cpp, line 629. Stopping when a memory value changes:

(gdb) print desktop $2 = (SPDesktop *) 0x33a0710 (gdb) awatch *0x33a0710 Hardware access (read/write) watchpoint 4: *0x33a0710 Listing breakpoints:

(gdb) info break Num Type Disp Enb Address What 1 breakpoint keep y 0x0000000000f64ab7 in Inkscape::UI::Tools::SelectTool::root_handler(_GdkEvent*) at ../../src/ui/tools/select-tool.cpp:460 2 breakpoint keep y 0x00007ffff03a4a30 exception throw 3 breakpoint keep y 0x0000000000f657a5 in Inkscape::UI::Tools::SelectTool::root_handler(_GdkEvent*) at ../../src/ui/tools/select-tool.cpp:629

       stop only if group_at_point == 0

4 acc watchpoint keep y *0x33a0710 Disabling breakpoints:

(gdb) disable 4 Deleting breakpoints:

(gdb) delete 3 Creating breakpoints that will only be stopped on once:

(gdb) tbreak foo::bar (gdb) tcatch throw Evaluating expressions If GDB can figure out what you are talking about, it can print pretty much anything. GDB also is immune to the private boundary of a class.

(gdb) print arc_context->arc $3 = (SPGenericEllipse *) 0x3afb610 A handy feature to try to determine if a heap object still exists (hasn't been delete()d yet) is to use the new GDB command info vtbl:

(gdb) print UXManager::getInstance() $4 = (Inkscape::UI::UXManager *) 0x3b6f1d0 (gdb) info vtbl $4 vtable for 'Inkscape::UI::UXManager' @ 0x136e500 (subobject @ 0x3b6f1d0): [0]: 0xbc7720 <Inkscape::UI::UXManagerImpl::~UXManagerImpl()> [1]: 0xbc7740 <Inkscape::UI::UXManagerImpl::~UXManagerImpl()> [2]: 0xbc81e0 <Inkscape::UI::UXManagerImpl::addTrack(SPDesktopWidget*)> … Here's what a delete()d object's vtable might look like:

(gdb) call 'operator delete'($4) (gdb) info vtbl $4 vtable for 'Inkscape::UI::UXManager' @ 0x3f27f80 (subobject @ 0x3b6f1d0): [0]: 0x190 [1]: 0x20 [2]: 0x3d91db0 [3]: 0x0 [4]: 0x448d40 <g_free@plt> …