-Wall , implicit declaration of function âtimeâ?

[javaeyes]

I finally took everyone's advice and compiled with -Wall. I whittled down 30 warnings to just 2, and I'm not sure what they mean.

1) implicit declaration of function âtimeâ

 srand ( (unsigned)time ( NULL ) );

2) implicit declaration of function âtoupperâ

firstletter[0] = toupper(tempoption->companyname[0]);

I'm sure it's something simple. But I can't see it.

[rags_to_riches]

man time
man toupper

Note the #includes

[grumpy]

time() is declared in <time.h>. toupper() is declared in <ctype.h>. rand() is declared in <stdlib.h>.

If you fail to #include those headers, the C compiler does not see all of the declarations. It therefore implicitly assume they are all functions that accept a variable argument list and return int.

The solution is to #include all of the standard headers needed.

Incidentally, googling for "C implicit declaration" provides pages of links with answers to this type of question.

[javaeyes]

Got it. No more warnings. sorry to bother.