Simeon Pilgrim

Our legacy C++ codebase once was a C codebase.  Way back then, there was no standard boolean type.  So in the wisdom of the day a type was declared

typedef int tBool;

The major problem with tBool’s is that over time enums, #define or magic constants get assigned to them, or they can be compared to said enums, #defines or magic constants, as they are all int’s.

Which works, but years later *somebody* came along and replaced the tBool for bool, and we started getting issues.

Now as in a lot of large codebases there tends to be a large amount of ignored warnings, and not enough daylight hours to remove them all.

So given that, and that your using Visual Studio 2005, here are the ones you should find and remove.

#define NON_BOOL_DEFINE 42
bool boolValue;

boolValue = NON_BOOL_DEFINE;

Warning C4305: ‘=’ : truncation from ‘int’ to ‘bool’

if( boolValue == NON_BOOL_DEFINE )

Warning C4806: ‘==’ : unsafe operation: no value of type ‘bool’ promoted to type ‘int’ can equal the given constant

Another hint your boolean types are being used wrong is this warning

Warning C4800: ‘const int’ : forcing value to bool ‘true’ or ‘false’ (performance warning)

I have just spent the last hour bashing my head, trying to workout why some new C++ code (to my project) was crashing.

I was constructing one class, and it was building some worker classes and crashing in the std::vector code when the worker class was being destroyed.

It just wasn’t making sense.

Why would code that’s been running for another team for over a year, blow-up when I use it?

I turned to a co-worker, described what was happening and said “it’s like some memory corruption or packing issue”

And it was a structure packing alignment issue. The imported project had default packing (8), and my really old solution uses packing (1), so somewhere the default class functions where getting generated with different opinions from where member’s were….

#pragma pack(push)
#pragma pack(4)
#pragma pack(pop)

to the rescue, and low and behold the problems gone. I hate this type of issue. Importing existing C++ projects happens so infrequently that this issue is not on the must check list. Where-as I was convinced I had fluffed up the usage of the new code….

I solved the 110502 Reverse and Add problem today. The hardest part was whipping up the worker functions to do text based numbers.

I started by laying out the algorithm in function blocks, then proceeded to full in the gaps. I had two bugs

1. my is_palindrome function didn’t have a default return value. It was C++ but even that seems a bit broken, but it compiled!
2. my data structure could hold 10 digits (ie 1,234,567,890) as the problem stated, but that didn’t seem enough. Size 100 fixed that.

I haven’t done any simple problem work for a while, and I like the idea of doing some of the Rudy Quiz (albeit in C#), yet the testing structure of Programming Challenges site makes it a contained experience.