succ raise OverflowDefect, succ does not handle unsigned integers correctly

[haoyu234]

Description

succ does not handle unsigned integers correctly.

let v = high(uint) div 2
echo v # 9223372036854775807
echo v + 1 # 9223372036854775808
echo succ v # Error: unhandled exception: over- or underflow [OverflowDefect]

N_LIB_PRIVATE NIM_CONST NU v__t1_u5 = ((NU)IL64(9223372036854775807));
nimln_(16);	colontmpD__2 = dollar___systemZdollars_u14(((NU64) ((NU)((NU64)(v__t1_u5) + (NU64)(((NU)1))))));
nimln_(17);	if (nimAddInt(v__t1_u5, ((NI)1), &TM__RKFvtxDChgOSG9c3eaEfBVA_2)) { raiseOverflow(); goto LA1_;

https://play.nim-lang.org/#pasty=XDlRYyZz

Nim Version

Nim Compiler Version 2.1.9 [Linux: amd64]
Compiled at 2024-07-25
Copyright (c) 2006-2024 by Andreas Rumpf

git hash: c1f91c2
active boot switches: -d:release

Current Output

9223372036854775807
9223372036854775808
/root/repos/iobuf/t1.nim(17) t1
/root/.choosenim/toolchains/nim-#devel/lib/system/fatal.nim(53) sysFatal
Error: unhandled exception: over- or underflow [OverflowDefect]

Expected Output

9223372036854775807
9223372036854775808
9223372036854775808

Possible Solution

No response

Additional Information

No response

[haoyu234]

The following changes seem to fix the issue.

  #define nimAddInt64(a, b, res) __builtin_add_overflow(a, b, res)
  #define nimSubInt64(a, b, res) __builtin_sub_overflow(a, b, res)
  #define nimMulInt64(a, b, res) __builtin_mul_overflow(a, b, res)

  #define nimAddInt(a, b, res) __builtin_add_overflow(a, b, res)
  #define nimSubInt(a, b, res) __builtin_sub_overflow(a, b, res)
  #define nimMulInt(a, b, res) __builtin_mul_overflow(a, b, res)

the test:

discard """
  targets: "c cpp"
"""

# Bug #23894

proc checkSucc(tp: typedesc) =
  let v = high(tp)
  let v2 = tp(uint64(v) div uint64(2))
  let v3 = succ v2
  discard v3

proc checkSuccOverflow(tp: typedesc) =
  let v = high(tp)
  try:
    let v2 = succ v
    discard v2
  except OverflowDefect:
    return

  doAssert false, "unreachable"

block: # overflow

  checkSuccOverflow(char)
  checkSuccOverflow(cint)
  checkSuccOverflow(cuint)
  checkSuccOverflow(csize_t)

  checkSuccOverflow(uint)
  checkSuccOverflow(uint8)
  checkSuccOverflow(uint16)
  checkSuccOverflow(uint32)
  checkSuccOverflow(uint64)

  checkSuccOverflow(int)
  checkSuccOverflow(int8)
  checkSuccOverflow(int16)
  checkSuccOverflow(int32)
  checkSuccOverflow(int64)

  checkSuccOverflow(cint)
  checkSuccOverflow(cuint)
  checkSuccOverflow(csize_t)

block: # should't overflow

  checkSucc(char)
  checkSucc(cint)
  checkSucc(cuint)
  checkSucc(csize_t)

  checkSucc(uint)
  checkSucc(uint8)
  checkSucc(uint16)
  checkSucc(uint32)
  checkSucc(uint64)

  checkSucc(int)
  checkSucc(int8)
  checkSucc(int16)
  checkSucc(int32)
  checkSucc(int64)