asm and std=c99 incompatibility

[danielclarke]

Calls to extended asm fail to compile with gcc when std=c99 compiler flag is set

Example

{.passC: "-std=c99".}

proc main =
  let src = 41
  var dst = 0

  asm """
    mov %1, %0\n\t
    add $1, %0
    : "=r" (`dst`)
    : "r" (`src`)"""

  echo dst

main()

Current Output

mtest.nim.c:104:5: error: expected ')'
    : "=r" (dst)
    ^
mtest.nim.c:102:5: note: to match this '('
        asm("    mov %1, %0\n\t\n"
           ^
1 error generated.

Expected Output

42

Possible Solution

I have a PR with the following change and a test, however this definitely feels out of my depth

In extccomp.nim, under compiler gcc:, replace

asmStmtFrmt: "asm($1);$n",

with

asmStmtFrmt: "__asm__($1);$n",

$ nim -v

Nim Compiler Version 1.7.1 [MacOSX: amd64]
Compiled at 2022-07-10
Copyright (c) 2006-2022 by Andreas Rumpf

git hash: e8ee2f9c2ad06cad2f62fe7505acbb43530f28d7

[danielclarke]

PR here: #20013