[BUG] Access Violation on invalid Align value
lazarus / 10-Designer

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Eugene Loza · 2017-09-08 16:08

Access Violation error on inputting an invalid Align value.

Steps to reproduce the bug:
1. Start a fresh Application.
2. Switch to Form Editor.
3. Put any control on the form (I've tested for TButton and TGroupBox)
4. Edit Align and delete a symbol there (e.g. alCustom -> lCustom)
5. Push Enter.
6. Get Access Violation Error
the Lazarus cannot work properly further, showing Access Violation
every time something is edited at the Form Editor.

Lazarus 1.8.0RC3 FPC 3.0.3 Debian Jessie 64 bit.

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Almir.Bispo · 2017-09-08 18:42

This is not a bug,but a bad use.Don't put a empty value because is not
permited

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Noodly · 2017-09-08 18:57

@Almir.Bispo

Any program that crashes for any reason has a bug - except O/S or
hardware failure.

All programs should cater for any input or sequence of events without
crashing and at the very worst show an accurate error message before
gracefully exiting.

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SunyD · 2017-09-08 19:35

I can't confirm that with Lazarus 1.6.4 and 1.8 RC 4 on windows 7.
When I write wrong value i.e. lcustom or blabla it changes to
alCustom.
Maybe Linux or gtk problem.

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wp · 2017-09-08 21:37

Quote from: Soner A. on September 08, 2017, 09:35:16 pmI can't confirm
that with Lazarus 1.6.4 and 1.8 RC 4 on windows 7.
When I write wrong value i.e. lcustom or blabla it changes to
alCustom.
Maybe Linux or gtk problem.
Same behavior (i.e., no error) on Linux Mint 18.1 KDE 32-bit / Laz
trunk / fpc 3.02

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howardpc · 2017-09-08 21:51

Seems to be a gtk 64-bit-related bug. Happens for me 'reliably' with
Mint 18 64-bit.

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Jurassic Pork · 2017-09-08 22:31

hello,
on LUBUNTU 16.04  64 bits gtk2 Lazarus 1.8RC3, the first time i try to
put a wrong align property i have a small error dialog window with the
message access violation but no crash and after to have validate this
dialog window no more error.

Friendly, J.P

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JuhaManninen · 2017-09-10 10:13

Quote from: Noodly on September 08, 2017, 08:57:19 pmAny program that
crashes for any reason has a bug - except O/S or hardware failure.
True, such unhandled Access Violation is always a bug.
It was reproducible. It did not depend on widgetset nor OS nor CPU
architecture. Only setting all debug compiler flags for building
Lazarus IDE affected. Then more likely an exception was raised instead
of doing something unpredictable later.

I fixed it in r55831 in trunk. Please test. If there are no negative
side-effects, it will be merged to 1.8.
Interestingly my fix actually reverts r185 by Marco from 2001-02-19,
which had message:
 "* Fix from maillist."
The "exit" is needed in TEnumPropertyEditor.SetValue when an invalid
value is given.
Maybe it was commented out because the Combobox in OI was then read-
only and valid values only could be selected.(?)
I don't think Marco remembers the details either, it has been over
16.5 years...

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guest58172 · 2017-09-10 12:51

Quote from: Eugene Loza on September 08, 2017, 06:08:42 pmAccess
Violation error on inputting an invalid Align value.

Steps to reproduce the bug:
1. Start a fresh Application.
2. Switch to Form Editor.
3. Put any control on the form (I've tested for TButton and TGroupBox)
4. Edit Align and delete a symbol there (e.g. alCustom -> lCustom)
5. Push Enter.
6. Get Access Violation Error
the Lazarus cannot work properly further, showing Access Violation
every time something is edited at the Form Editor.

Lazarus 1.8.0RC3 FPC 3.0.3 Debian Jessie 64 bit.

Before creating a duplicated entry, this is the bug:

https://bugs.freepascal.org/view.php?id=29240

It's actually a more generic problem related to TI controls.

____

A workaround is to use a setter that verifies the value when you
publish an enum property. (must be >= low(Stuff) and <= high(Stuff)).
Unfortunately this only possible for custom components and other
persistents.

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JuhaManninen · 2017-09-10 18:35

r55831 will be merged to 1.8.
In r55832 I changed the logic so that OI shows '(Invalid)' instead of
the old restored value when an invalid enum value is typed.
What do you think?