From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.1) Gecko/20021003 Description of problem: man isblank, gives usage or "isblank()", yet the following program yields at error when compiled (warning actually, but it shouldn't). #include <ctype.h> int main() { char a; int i = isblank(a); return(i); } # gcc -Wall -o fooey foo.c foo.c: In function `main': foo.c:5: warning: implicit declaration of function `isblank' Note: isblank() should NOT be seen by the compiler as "implicitly defined" Version-Release number of selected component (if applicable): How reproducible: Always Steps to Reproduce: 1. See sample code snippet above 2. 3. Actual Results: erroneous warning message. Note that w/o proper prototyping, compile time argument mismatches would be properly converted to correct argument type. Expected Results: no warning message. Additional info: This same bug existed in Red Hat 7.3
Please RTFM info libc about feature set macros. isblank is only specified in ISO C99, so you either get it when compiling with -std=c99, -std=gnu99 or -D_ISOC99_SOURCE.