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I inherited some code which contains far too many ...
I inherited some code which contains far too many #ifdef's for my taste. How can I preprocess the code to leave only one conditional compilation set, without running it through the preprocessor and expanding all of the #include's and #define's as well? There are programs floating around called unifd...
2016-01-29, 1050👍, 0💬

People keep saying that the behavior of ...
People keep saying that the behavior of i = i++ is undefined, but I just tried it on an ANSI-conforming compiler, and got the results I expected. A compiler may do anything it likes when faced with undefined behavior (and, within limits, with implementation-defined and unspecified behavior), includi...
2015-11-18, 1050👍, 0💬

What is the best style for code layout in C?
What is the best style for code layout in C? While providing the example most often copied, also supply a good excuse for disregarding it: The position of braces is less important, although people hold passionate beliefs. We have chosen one of several popular styles. Pick a style that suits you, the...
2015-05-18, 1050👍, 0💬

I have a pre-ANSI compiler, without stdarg.h What can I do?
I have a pre-ANSI compiler, without stdarg.h What can I do? There's an older header, &lt;varargs.h>, which offers about the same functionality. Here is the vstrcat function, rewritten to use &lt;varargs.h>: #include &lt;stdio.h> #include &lt;varargs.h> #include &lt;string.h> exte...
2015-06-10, 1049👍, 0💬

I have a program that seems to run correctly
I have a program that seems to run correctly, but it crashes as it's exiting, after the last statement in main(). What could be causing this? A:There are at least three things to look for: 1. If a semicolon in a previous declaration is missing, main might be inadvertently declared as returning a str...
2015-05-29, 1049👍, 0💬

Why do some people write if(0 == x) instead of if(x == 0)?
Why do some people write if(0 == x) instead of if(x == 0)? It's a trick to guard against the common error of writing if(x = 0) If you're in the habit of writing the constant before the ==, the compiler will complain if you accidentally type if(0 = x) Evidently it can be easier for some people to rem...
2015-05-15, 1047👍, 0💬

I have got this tricky preprocessing I want to do and I cant figure out a way to do it.
I have got this tricky preprocessing I want to do and I cant figure out a way to do it. C's preprocessor is not intended as a general-purpose tool. (Note also that it is not guaranteed to be available as a separate program.) Rather than forcing it to do something inappropriate, you might want to wri...
2016-01-19, 1045👍, 0💬

I keep getting errors due to library functions being undefined, but I am including all the right header files.
I keep getting errors due to library functions being undefined, but I am including all the right header files. In the general case of calling code in an external library, using #include to pull in the right header file(s) is only half of the story; you also have to tell the linker to search the exte...
2015-07-14, 1045👍, 0💬

I am getting baffling syntax errors which make no sense at all
I'm getting baffling syntax errors which make no sense at all, and it seems like large chunks of my program aren't being compiled. Check for unclosed comments, mismatched #if/#ifdef/#ifndef/#else/#endi fdirectives, and perhaps unclosed quotes; remember to check header files, too.
2015-06-01, 1045👍, 0💬

I have some old code that tries to construct identifiers with a macro like ...
I have some old code that tries to construct identifiers with a macro like #define Paste(a, b) a/**/b but it doesn't work any more. It was an undocumented feature of some early preprocessor implementations (notably Reiser's) that comments disappeared entirely and could therefore be used for token pa...
2016-01-27, 1043👍, 0💬

My ANSI compiler complains about a mismatch when it see
My ANSI compiler complains about a mismatch when it sees extern int func(float); int func(x) float x; { ... You have mixed the new-style prototype declaration ``extern int func(float);'' with the old-style definition ``int func(x) float x;''. It is usually possible to mix the two styles but not in t...
2016-01-13, 1043👍, 0💬

What does the message Automatic aggregate intialization is an ANSI feature mean?
What does the message Automatic aggregate intialization is an ANSI feature'' mean? My compiler is complaining about valid ANSI code. Messages like these are typically emitted by pre-ANSI compilers which have been upgraded just enough to detect (but not properly translate) new C features which were i...
2015-11-30, 1042👍, 0💬

I heard that you have to include stdio.h before calling printf. Why?
I heard that you have to include stdio.h before calling printf. Why? So that a proper prototype for printf will be in scope. A compiler may use a different calling sequence for functions which accept variable-length argument lists. (It might do so if calls using variable-length argument lists were l...
2015-06-17, 1042👍, 0💬

Dont ANSI function prototypes render lint obsolete?
Dont ANSI function prototypes render lint obsolete? Not really. First of all, prototypes work only if they are present and correct; an inadvertently incorrect prototype is worse than useless. Secondly, lint checks consistency across multiple source files, and checks data declarations as well as func...
2015-05-01, 1041👍, 0💬

Did C have any Year 2000 problems?
Did C have any Year 2000 problems? No, although poorly-written C programs might have. The tm_year field of struct tm holds the value of the year minus 1900; this field therefore contains the value 100 for the year 2000. Code that uses tm_year correctly (by adding or subtracting 1900 when converting ...
2015-08-03, 1040👍, 0💬

Interview question - Order Process Automation
An ecommerce transaction starts on an instance of SAP Hybris at the frontend (browser-based). The order then flows through a bespoke SQL Server based Data Hub, into MS Dynamics 365 (F&amp;O), where the order orchestrated. The flow also includes several batch jobs between the order placement and ...
2020-10-17, 1039👍, 1💬

💬 2020-10-17 FYIcenter.com: If you have the budget, replace all 3 systems with a single end-to-end, fully automated, eCommerce solution. If you want to keep...

Why are some ANSI ISO Standard library functions showing you
Why are some ANSI/ISO Standard library functions showing up as undefined, even though I've got an ANSI compiler? It's possible to have a compiler available which accepts ANSI syntax, but not to have ANSI-compatible header files or run-time libraries installed. (In fact, this situation is rather comm...
2015-11-30, 1038👍, 0💬

Why isnt my procedure call working? The compiler seems to skip right over it
Why isnt my procedure call working? The compiler seems to skip right over it Does the code look like this? myprocedure; C has only functions, and function calls always require parenthesized argument lists, even if empty. Use myprocedure(); Without the parentheses, the reference to the function name ...
2015-06-01, 1036👍, 0💬

What is the difference between const char .....
What's the difference between const char *p, char const *p, and char * const p? The first two are interchangeable; they declare a pointer to a constant character (you can't change any pointed-to characters). char * const p declares a constant pointer to a (variable) character (i.e. you can't change ...
2016-01-06, 1035👍, 0💬

People always say that good style is important
People always say that good style is important, but when they go out of their way to use clear techniques and make their programs readable, they seem to end up with less efficient programs. Since efficiency is so important, isn't it necessary to sacrifice some style and readability? It's true that g...
2015-05-06, 1035👍, 0💬

How can I specify a variable width in a scanf format string?
How can I specify a variable width in a scanf format string? You can't; an asterisk in a scanf format string means to suppress assignment. You may be able to use ANSI stringizing and string concatenation to construct a constant format specifier based on a preprocessor macro containing the desired wi...
2015-10-26, 1034👍, 0💬

How can I return a sequence of random numbers which dont repeat at all?
How can I return a sequence of random numbers which dont repeat at all? What you're looking for is often called a ``random permutation'' or ``shuffle.'' One way is to initialize an array with the values to be shuffled, then randomly interchange each of the cells with another one later in the array: ...
2015-07-24, 1034👍, 0💬

How can I shut off the warning ...
How can I shut off the ``warning: possible pointer alignment problem'' message which lint gives me for each call to malloc? A modern lint shouldn't be complaining about this. Once upon a time, lint did not and could not know that malloc ``returns a pointer to space suitably aligned for storage of an...
2015-05-05, 1033👍, 0💬

How can I sort a linked list?
How can I sort a linked list? Sometimes it's easier to keep the list in order as you build it (or perhaps to use a tree instead). Algorithms like insertion sort and merge sort lend themselves ideally to use with linked lists. If you want to use a standard library function, you can allocate a tempora...
2015-08-10, 1032👍, 0💬

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