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Category: Tools

Install Clang and Visual Studio Code on Ubuntu

Posted on April 15, 2020December 2, 2020 by David

Clang is very easy to install. Open a terminal and issue this command:

sudo apt install clang

It takes a little bit more for Visual Studio Code (aka VS Code). Start on the download page of VS Code. Just google for download Visual Studio Code or click here. Click the Deb rectangle and pick the Open with Software install (default) and that will install it.

After that is installed, run VS Code (open a terminal and type code) and click the extensions icon (5th down on the left) and type in C++ in the search box. The first result is by Microsoft so select it and click install.

Now I created a Projects folder under my home, so click on open Folder in the File menu and select Projects. You can create individual folders for applications under that. If you look closely you can see Asteroids, AsteroidsDND and Examples with Asteroids being open and containing two .c files.

To compile, make sure the open tab is the file you wish to compile then click Terminal on the top menu and Run Build Task… You’ll see the compiled programs on the left under the Asteroids folder (decnot and ex1).

There’s a bit more for configuring Builds and Debugging but I’ll cover that another time.

How I write my ebooks

Posted on April 13, 2020April 3, 2020 by David

My secret: is I use a piece of software called Jutoh from a Scottish software house. It costs £35 and if you are writing a book or e-book I highly recommend it.

Note I have no connection with them except as a very satisfied customer.

It’s all the little things, inserting pictures, tables, handling source code that make it particularly good for non-fiction books.

It also includes formatting for various programming languages and is cross-platform with versions for Linux, Mac and Windows.

The current version of the Linux e-book has 55144 words, (307407 characters). It takes about 10 seconds to compile that into a .mobi (Amazon) or .epub file with all sorts of warnings.

Originally I started writing the first e-book in a text editor then imported it to MS-Word. But Word is not exactly great software for publishing non-fiction as it’s not desktop publishing. Actually you don’t need desktop publishing per se because Kindle reflows the text, but having pictures, source code and tables makes it more complicated.

I looked about, found Jutoh and consider myself very fortunate; it makes life much easier. I’ve also had excellent support from Jutoh’s creator Dr. Julian Smart who is also well known as a creator of wxWidgets.

Writing an e-book is a multi-pass project that takes me roughly 3-4 months part-time.

Pass 1. Develop the software and e-book structure i.e. chapters.
Pass 2. Write the chapters.
Pass 3. Look for typos. For now this is just me, but eventually I hope to be able to afford a technical editor.
Pass 4. Tidy up the layout. This is probably the slowest phase. Because of the images, tables and shortish code listings, it might look neat and tidy at one size, but if you change the viewing font size, it looks er not quite so neat! I can’t see any way round that.

A friend drew the original book cover but I’ve decided to pay for the cover for the Linux version.

How to view disassembled C/C++ code in Visual Studio Code

Posted on April 9, 2020April 3, 2020 by David

There are four steps to do this. That’s assuming that you have successfully compiled your C or C++ program and have the source file handy.

Install Disassembly Explorer extension into Visual Studio Code.
Set a configuration setting.
Run a single line command in terminal.
Select a command in the Visual Studio Code command palette.

Install Disassembly Explorer.

In Visual Studio Code just switch to the extension tab and search for Dissassembly Explorer and click the install button.

Next is configuration

View the installed extensions and click the cogwheel for Disassembly Explorer then click Extension Settings at the bottom of the popup menu. A Settings tab will open, click Edit in settings.json.

You should see a few settings but only this one matters: “compilerexplorer.compilationDirectory”: “${workspaceFolder}/.vscode” . That path is where the compile etc. .json files are located.

Now open a terminal

I’ve assumed that you are running on Linux or Mac. If you are on Windows, you can also use Visual Studio Community Edition which includes disassembly features and why I’m not mentioning it here.

In the folder with your source files issue this command in the terminal.

clang -g -o asteroids.S -S asteroids.c

If OTOH you are running gcc then just substitute gcc for clang.

Finally, back in Visual Studio Code select your source file as the open tab then press F1 and in the menu that appears type in enough of Disassembly Explorer: Show until you can select it and a second tab should open with the disassembly. Click on a function in the source tab and it will jump to the correct place in the disassembled code.

Visual Studio Vs Visual Studio Code?

Posted on April 3, 2020April 3, 2020 by David

I wrote the first book on Windows and used Visual Studio Community Edition 2017 (VS). For Linux I’m using Visual Studio Code (VSC) but if you are working on Windows you have the choice. So which is better suited to you?

Disassembly of OutputDebugString program

Given that my full time job involved Visual Studio Professional, it wasn’t a difficult choice for me, though having used VSC on Linux, I’m now warming to it.

I found the configuration messy but if you stick at it, you get there. It’s a fairly simple product but once you get into all the configuration and extensions, there’s a lot more to it.

VS (now at 2019 version) is an excellent tool and the navigation features and debugging are better than VSC. You can also view disassembly of C code as the screenshot shows.

But if you are also working on Linux or Mac and using VSC, it might be easier or at least more consistent using it for all platforms. Mind you there’s also the question of MSVC vs Clang to sort as well.

VS has extensions but only 3271 currently compared to 16934 for VSC and many of the VS extensions are trial while it appears that all of VSC are free. There’s also nearly ten times as many programming language extensions for VSC (3427) compared to VS (351).

So there’s no outright clear winner here. YMMV as the saying goes. (Your mileage may vary). Here for your delectation is that disassembly including the original C lines. Don’t worry, I won’t publish too many of these!

int main()
{
00E31700  push        ebp  
00E31701  mov         ebp,esp  
00E31703  sub         esp,0CCh  
00E31709  push        ebx  
00E3170A  push        esi  
00E3170B  push        edi  
00E3170C  lea         edi,[ebp-0CCh]  
00E31712  mov         ecx,33h  
00E31717  mov         eax,0CCCCCCCCh  
00E3171C  rep stos    dword ptr es:[edi]  
00E3171E  mov         ecx,offset _1EF31893_ods@c (0E3C00Ch)  
00E31723  call        @__CheckForDebuggerJustMyCode@4 (0E3120Dh)  
    wchar_t * text=L"Hello World!\n";
00E31728  mov         dword ptr [text],offset string L"Hello World!\n" (0E37B30h)  
    OutputDebugString(text);
00E3172F  mov         esi,esp  
00E31731  mov         eax,dword ptr [text]  
00E31734  push        eax  
00E31735  call        dword ptr [__imp__OutputDebugStringW@4 (0E3B000h)]  
00E3173B  cmp         esi,esp  
00E3173D  call        __RTC_CheckEsp (0E31217h)  
}
00E31742  xor         eax,eax  
00E31744  pop         edi  
00E31745  pop         esi  
00E31746  pop         ebx  
00E31747  add         esp,0CCh  
00E3174D  cmp         ebp,esp  
00E3174F  call        __RTC_CheckEsp (0E31217h)  
00E31754  mov         esp,ebp  
00E31756  pop         ebp  
00E31757  ret

Logging on Windows – OutputDebugString

Posted on April 2, 2020March 24, 2020 by David

In the post about rsyslog three days ago, I explained how to log from Linux programs using the rsyslog daemon.

It’s slightly different in Windows. There’s a built in function called OutputDebugString(LPCWSTR str) that you can call from anywhere in your program. It dumps the string str into the Output window if you are debugging it in Visual Studio.

If you are running this outside of a debugger, the output is lost unless you can capture it with a suitable utility. DebugView from SysInternals.com (it redirects to Microsoft) is one such utility. That’s a screenshot of it below.

Just run DebugView and leave it there. It might catch other stuff from Windows, but when you run your program from the command line or double click on it, it will execute quickly and you’ll see any strings captured like this one.

This is the program that I ran. In Release it compiles to a 9 KB exe! Because OutPutDebugString needs a LPCWSTR (Long Pointer to a WideString), I declared the text as wchar_t.

#include <Windows.h>

int main()
{
    wchar_t * text=L"Hello World!\n";
    OutputDebugString(text);
}

At work I developed a very large program that only worked running on another computer. I used OutputDebugString extensively and without it, debugging would have been much harder.

Using rsyslog to log

Posted on March 30, 2020March 23, 2020 by David

I’m a great fan of logging; it helps you find out what’s happening in a program even if you can’t debug it. Linux, well Ubuntu has a service (sorry Daemon!) called rsyslog that logs messages from all sorts of processes and it’s quite easy to use in our programs as well.

If we don’t do the next steps all the log messages will go into a file called syslog in /var/log and as this gets a lot of stuff it can grow reasonably quickly. But if you do the following steps, all logged output will instead go into

/var/log/asteroids.log.

From a terminal type the following command:

sudo gedit /etc/rsyslog.d/30-debugging.conf

Type this in and then save it (click the Save button) and close gedit.

if $programname == 'asteroids' then /var/log/asteroids.log
& ~

Now run this command:

sudo service rsyslog restart

It should return immediately and means that any logging to syslog from a program called asteroids will from now on be redirected to /var/log/asteroids.log.

Using rsyslog in a C program

Here’s a short C Program that puts a message in the asteroids file.

#include <syslog.h>
#include <stdio.h>

int main() {
    openlog("asteroids",LOG_CONS | LOG_PID | LOG_NDELAY, LOG_USER);    
    syslog(LOG_INFO,"Test Message %d",1);
    closelog();
}

In a typical program you’d put the openlog statement in main() near the start and the closelog() near the end of main, and uses as many syslog() calls throughout your program as you need.

Now what I suggest you do is open another terminal and run this command before you run your main program. This will just sit there printing out each message line as it appears in asteroids.log. You can stop tail by hitting ctrl-c.

tail -f /var/log/asteroids.log

H/T to this StackExchange answer from almost 8 years ago and answer by giuspen.

A tale of two diffs

Posted on March 27, 2020March 22, 2020 by David

I’ve used diff and merge tools since the year dot. They let you compare two files and see on what lines they differ. You can also copy individual or blocks of lines from one to the other; that’s the merge. My all-time favourite was the commercial Araxis Merge which did a three way comparison and could be controlled by COM. I did this to compare two code bases.

Ten years earlier code for Base Metals (commodities trading) had been forked from Oil Trading software. There were ten years of changes to both sets of code and my job was to merge them back into one code base. I wrote a program to walk Araxis Merge through all folders of both code sets and out-put the differences, Then I could start merging where they differed. It still took about two months but I couldn’t have done it as quick without Araxis.

However most of us don’t have access to Enterprise tools, so here are two alternatives. The first is Devart’s Code Compare (that’s the image above) and the second is a free Extension for Visual Studio Code called Diff & Merge. I’ve added both to the Links to C utilities page.

New page added to Website

Posted on March 25, 2020March 21, 2020 by David

I thought it about time to add a list of curated C utilities such as compilers, IDES etc. So you’ll see that bar under the title now includes Links To C Utilities.

One of the included links is to Cheerp which is a C/C++ compiler that can output WebAssembly. One of my goals is to add a WebAssembly chapter to my first EBook, after the 2nd one on Linux is done. I want to play my asteroids game in the browser.

I have used EmScriptem to do this but I’d like to see what other tools are available.

I’m considering switching to C11

Posted on March 16, 2020March 12, 2020 by David

Programming image — Image by Gerd Altmann from Pixabay

All C code I write in the books is currently to the C99 standard. All the compilers involved (Visual C++ on Windows and Clang on Ubuntu) support C99 but C11 support seems restricted to GCC and Clang.

Microsoft has traditionally supported C++ but their C support seems a bit grudging; realistically they don’t prioritise it which I can understand.

Given though that I’m not going to republish my first e-book for a while (I’d like to add a WebAssembly chapter or two first), I’m going to investigate whether it’s worth switching to C11 for the 2nd book. From what I’ve read all it needs is a flag to tll it to compile to C11 standards. This is for Clang.

-std=c11

But the other question is what will I gain by doing this and I can’t actually see there’s that much benefit.. I don’t need Unicode, I don’t think alignment will really make much difference. You can read about the C11 changes on WikiChip.

So I’ve made the decision. I’ll stick with C99 for now. But for an alternative view, I recommend Danny Kalev’s 2012 article on C11.

I do like Visual Studio Code

Posted on March 11, 2020March 22, 2020 by David

When I wrote the Windows version of the book I used Visual Studio and it was quite excellent. But Visual Studio Code (VSC), the free cross-platform IDE is also very impressive.

Not only does it let you create your own extensions but you can even include debugging and visual debugging like Visual Studio.

I installed Clang and it’s associated debugger lldb. It is pretty powerful, The only thing that is a bit difficult with VSC is the learning curve for configuring builds, etc. With the Microsoft C/C++ extension there are four JSON files that must be configured for compiling, debugging etc.

The picture is from the website for the Visual Studio code marketplace. There are currently over 16,000 extensions most if not all (I haven’t checked them all!) are free and support virtually every popular programming language and probably one or two I haven’t heard of.