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I write all my C and C++ code at warning level 4 (the maximum, which is probably equivalent to -Wall). IMO, it was a mistake for Visual Studio to default to wa
by palish 15y ago
I write all my C and C++ code at warning level 4 (the maximum, which is probably equivalent to -Wall). IMO, it was a mistake for Visual Studio to default to warning level 3. Ignoring the compiler in production code is a sign of laziness, or that you don't take what you're doing seriously.
Warnings should be disabled on a per-source-file basis. And since you actively choose to ignore specific warnings, you still benefit from the compiler's other sanity checks.
In Visual Studio, this is accomplished by
#pragma warning( disable: 4100 )
at the top of a .c or .cpp file. This will ignore "unreferenced parameter" warnings. (Personally, I don't ignore those either. It's saved me on more than one occasion, and once is enough for me. So instead, I use a macro UNREF_PARAM(param) to suppress the warning in specific cases.)
A header file sometimes generates a warning that you want to choose to ignore. But if we disabled it in the header file, then that disable would propagate to all other code which included the header file -- a big mistake!
Visual Studio solves this by:
#pragma warning( push )
#pragma warning( disable: 4100 )
//----------------------------------------------------
// foo.h
// The Foo module serves as an example of how to
// properly suppress the "unreferenced parameter"
// warning within a header file, via Visual Studio's
// #pragma warning( push ) and pop mechanism.
//----------------------------------------------------
/*
.... code which generates the warning ....
*/
#pragma warning( pop )
This allows you to "scope" the disable to a single header file.
(Lastly, it's worth noting that SQLite outputs hundreds of warnings --- but they are neither lazy nor irresponsible, because they have hundreds of unit tests to verify that SQLite works correctly at runtime, as defined by the tests, across all platforms.)
- burgerbrain 15y agoSurely there is such a thing as a piece of code that generates very legitimate warnings, but happens to compile to something that appears to work under at least most circumstances. Ignoring compiler warnings does seem pretty irresponsible to me, no matter how superb your unit test coverage is. At the very least it will cause a degregation of the codebase over time.
- pestaa 15y agoAnd how exactly could SQLite benefit from warning-free compilation? It not only appears to work but it does its job pretty well. Unit tests prove a different level of semantics that these warnings cannot substitute (although possibly complement).
- palish 15y agoTests and warnings compliment each other nicely. "My, you're looking testy today!" ... burgerbrain points out something very important: Code bases with warnings tend to be degenerate. Tend to. SQLite is not one of them. But I've seen several large codebases. The two which were beautiful also had zero warnings, and the ~dozen others ranged from "meh" all the way down to "lol, grab a snickers". This is obviously not enough data to draw any meaningful statistical conclusions from --- but it would be silly to ignore it completely. Good C/C++ programmers tend to respect compiler warnings.
- awj 15y ago> Unit tests prove a different level of semantics that these warnings cannot substitute (although possibly complement). That, actually, is part of the point. Unit tests check for correct expression of the problem domain (and solution). Compiler warnings check for correct expression of language constructs. It's possible, though not usually likely, for incorrect language usage to mask incorrect implementations.
- palish 15y ago"Surely there is such a thing as a piece of code that generates very legitimate warnings, but happens to compile to something that appears to work under at least most circumstances." Yes. The most trivial example is probably (C++): Foo* foo = malloc( sizeof(Foo) ); // warning: void* to Foo* But this is entirely valid as long as Foo is a POD type, or as long as you use placement new afterwards. The most annoying warning ever is probably: while ( true ) // warning: conditional expression is constant { foo(); if ( bar() ) break; baz(); } Thanks, compiler! <facepalm> It's silliness like this which has caused many people to kneejerk ignore every warning ever. But in doing so, they don't realize they're throwing away a lot of free data about their codebase, while also encouraging dangerous coding practices.