imaxabs / imaxdiv / uabs / ulabs / ullabs / umaxabs (3) - glibc

Split from the chapter glibc: arithmetic functions into the per-function layout; see the method page and the glibc ledger for coverage status.

Declaration and gates

#include <inttypes.h>

intmax_t imaxabs(intmax_t n);
typedef struct { intmax_t quot, rem; } imaxdiv_t;
imaxdiv_t imaxdiv(intmax_t numer, intmax_t denom);

/* ISO C2Y family, documented in the manual, not yet in host headers: */
unsigned int       uabs(int n);              /* stdlib.h */
unsigned long      ulabs(long n);            /* stdlib.h */
unsigned long long ullabs(long long n);      /* stdlib.h */
uintmax_t          umaxabs(intmax_t n);      /* inttypes.h */

imaxabs/imaxdiv are unconditionally declared in /usr/include/inttypes.h (lines 351 and 354; imaxdiv_t typedef lines 331-345). The C2Y unsigned family appears in the manual with exactly the signatures above (arith.texi lines 1237-1244, 1248-1256) but is absent from both /usr/include/stdlib.h and /usr/include/inttypes.h on this host (grep verified), and from nm -D libc.so.6.

Semantics

imaxabs returns the absolute value of its intmax_t argument (abs(3), which covers imaxabs via link). As with abs, the absolute value of the most negative integer is undefined; the manual adds that using uabs avoids that two’s-complement hazard for int (arith.texi lines 1257-1261). imaxdiv computes quotient and remainder at once: the result r satisfies r.quot*denominator + r.rem == numerator, quotient rounded toward zero, remainder taking the sign of the numerator; division by zero is undefined behavior (manual, node Integer Division, arith.texi lines 146-152, 256-268). imaxdiv was added in C99 (arith.texi line 265).

Gotchas and portability

• imaxabs is a weak alias of labs on this LP64 host (nm shows both at one address) – true wherever intmax_t is long.
• The four unsigned names are the only rows on this page whose glibc 2.41 support is manual-only: no header declaration and no exported symbol; treat code using them as forward-looking C2Y.
• musl 1.2.5: imaxabs/imaxdiv present (musl include/inttypes.h lines 16-17); the unsigned family is absent (verified). The abs/div page covers the int/long/long long siblings.

References

• glibc manual: arith.texi, nodes Absolute Value (lines 1223-1270), Integer Division (lines 128-268)
• man3: abs(3) (covers imaxabs), div(3) (covers imaxdiv)
• headers: /usr/include/inttypes.h
• symbols: nm -D --with-symbol-versions libc.so.6