коментарии после кода в строке поместить в новую строку над

#include <stdio.h>
#include <string.h>
#include <assert.h>

static void handle_line(char *b, char const *eoln, char const *def_eoln);
int main(void) {
#define MAX_LINE_LEN 100000
  static char b[MAX_LINE_LEN];

  char * p;
  char const *eoln, *def_eoln;
  def_eoln = "\n";
  while(fgets(b,sizeof(b),stdin)) {
    p = strchr(b,'\n');
    if(p) {
      assert(!p[1]);
      if(p!=b && *(p-1)=='\r') { eoln = "\r\n"; *(p-1) = 0; }
      else { eoln = "\n"; *p = 0; }
      def_eoln = eoln;
    } else eoln = "";
    handle_line(b, eoln, def_eoln);
  }
  return 0;
}

static void handle_line(char *b, char const *eoln, char const *def_eoln) {
  size_t p, plen;
  char c, q;
  for(p=0; (c=b[p])==' ' || c=='\t'; p++);
  plen = p;
  q = 0;
  while(c = b[p]) {
    if(q) {
      p++;
      if(c==q) q=0;
      else if(c=='\\') { if(b[p]) p++; }
      continue;
    }
    if(c=='\'' || c=='"') { q=c; p++; continue; }
    if(c!='/' || b[p+1]!='/') { p++; continue; }
    if(plen) fwrite(b, 1, plen, stdout);
    fputs(b+p, stdout);
    fputs(def_eoln, stdout);
    while(p && (b[p-1]==' ' || b[p-1]=='\t')) p--;
    if(p) { fwrite(b, 1, p, stdout); fputs(eoln, stdout); }
    return;
  }
  fputs(b, stdout); fputs(eoln, stdout);
}

#include <stdio.h>
#include <ctype.h>

#define BUFLEN 10000

int main(void)
{
        char buf[BUFLEN];
        while (fgets(buf, BUFLEN, stdin)) {
                int i, nsp;
                for (nsp = 0; isspace(buf[nsp]); nsp++);
                for (i = nsp; buf[i] != '\0'; i++) {
                        if (buf[i] == '/' && buf[i + 1] == '/') {
                                fwrite(buf, nsp, 1, stdout);
                                printf("%s", buf + i);
                                buf[i] = '\n';
                                buf[i + 1] = '\0';
                                break;
                        }
                }
                printf("%s", buf);
        }
        return 0;
}

   printf("some // text // literal");

   // text // literal");
   printf("some

sed 's:^\([[:space:]]\)\(.*\)\(\/\/.*\)$:\1\3\n\1\2:'
sed 's:^\(\([[:space:]]\).*\)\(\/\/.*\)$:\2\3\n\1:'

#include <stdio.h>
#include <ctype.h>
#include <string.h>

#define BUFLEN 10000

int main(void)
{
        char buf[BUFLEN];
        while (fgets(buf, BUFLEN, stdin)) {
                int i, nsp, nq = 0;
                for (nsp = 0; isspace(buf[nsp]); nsp++);
                for (i = nsp; buf[i] != '\0'; i++) {
                        if (buf[i] == '"')
                                nq++;
                        if (nq % 2 == 0 && buf[i] == '/' && buf[i + 1] == '/') {
                                char *const cm = buf + i;
                                fwrite(buf, nsp, 1, stdout);
                                printf("%s", cm);
                                if (cm[strlen(cm) - 1] != '\n')
                                        printf("\n");
                                buf[i] = '\n';
                                buf[i + 1] = '\0';
                                break;
                        }
                }
                printf("%s", buf);
        }
        return 0;
}

  printf("some\" // literal"); // q

  // q
  printf("some\" // literal");

  // literal"); // q
  printf("some\"

$ echo "    код // есть ли готовые инструменты для такого?" | sed 's:^\([[:space:]]*\)\(.*\)\(\/\/.*\)$:\1\3\n\1\2:'
    // есть ли готовые инструменты для такого?
    код 

$ sed 's:^\([[:space:]]*\)\(.*\)\(\/\/.*\)$:\1\3\n\1\2:'
  printf("some\" // literal"); // comment // here

  // here
  printf("some\" // literal"); // comment 

#include <stdio.h>
int main(void) {
  /*
  printf("fail\n"); // */ printf("ok\n");
  return 0;
}

/* (c) firk; may use without restrictions */
#include <stdio.h>
#include <assert.h>
#include <string.h>

static void handle_line(char *b, char const *eoln, char const *def_eoln, char *pq, unsigned long ln, int warnq);

int main(int argc, char const * const * argv) {
#define MAX_LINE_LEN 100000
  static char b[MAX_LINE_LEN];
  char q;
  unsigned long ln;
  int warnq;
  char * p;
  char const *eoln, *def_eoln;
  
  warnq = !(argc>=2 && !strcmp(argv[1],"--multistring"));
  def_eoln = "\n";
  q = 0;
  ln = 0;
  while(fgets(b,sizeof(b),stdin)) {
    ln++;
    p = strchr(b,'\n');
    if(p) {
      assert(!p[1]);
      if(p!=b && *(p-1)=='\r') { eoln = "\r\n"; *(p-1) = 0; }
      else { eoln = "\n"; *p = 0; }
      def_eoln = eoln;
    } else eoln = "";
    handle_line(b, eoln, def_eoln, &q, ln, warnq);
  }
  if(ferror(stdin)) fprintf(stderr, "error reading input (last read line is %lu)\n", ln);
  if(q=='/') fprintf(stderr, "warning: unterminated multiline comment at EOF (last line is %lu)\n", ln);
  else if(q) fprintf(stderr, "warning: unterminated quoted (%c) entity at EOF (last line is %lu)\n", q, ln);
  return 0;
}

static void handle_line(char *b, char const *eoln, char const *def_eoln, char *pq, unsigned long ln, int warnq) {
  size_t p, plen;
  char c, q;
  char q0;
  
  for(p=0; (c=b[p])==' ' || c=='\t'; p++);
  plen = p;
  q = q0 = *pq;
  while(c = b[p]) {
    if(q=='/') {
      p++;
      if(c=='*' && b[p]=='/') { p++; q = 0; }
      continue;
    }
    if(q) {
      p++;
      if(c==q) q=0;
      else if(c=='\\') { if(b[p]) p++; }
      continue;
    }
    if(c=='\'' || c=='"') { q=c; p++; continue; }
    if(c=='/' && b[p+1]=='*') { q='/'; p+=2; continue; }
    if(c!='/' || b[p+1]!='/') { p++; continue; }
    /* found unquoted // */
    if(q0) {
      if(q0=='/') fprintf(stderr, "warning: can't safely reorder //-comment due to pending multiline-comment at line %lu beginning\n", ln);
      else fprintf(stderr, "warning: can't safely reorder //-comment due to pending quoted (%c) entity at line %lu beginning\n", q, ln);
      break;
    }
    /* here q0==0 && q==0 */
    if(plen) fwrite(b, 1, plen, stdout);
    fputs(b+p, stdout);
    fputs(def_eoln, stdout);
    while(p && (b[p-1]==' ' || b[p-1]=='\t')) p--;
    if(p) { fwrite(b, 1, p, stdout); fputs(eoln, stdout); }
    return;
  }
  /* found EOLN w/o // */
  fputs(b, stdout); fputs(eoln, stdout);
  *pq = q;
  if(warnq && q && q!='/') fprintf(stderr, "warning: unterminated quoted (%c) entity at line %lu\n", q, ln);
}

#include <stdio.h>
int main(void) {
/\
*
  printf("bad\n");  return 0; // */
  printf("good\n"); return 0;
}

sed -e 's/\(.*\)\(\/\/.*\)/\2\n\1/g'

$ echo "     // есть ли готовые инструменты для такого?" | sed '/^\s*[^ ].*\/\//s:^\([[:space:]]*\)\(.*\)\(\/\/.*\)$:\1\3\n\1\2:'

/* (c) firk; feel free to use for anything */
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

static char * wise_gets(char const * * eoln_type, unsigned long long * p_ln) {
  static char * buf;
  static size_t bs, bp, bl;
  static unsigned long long ln = 1;
  static int eof;
  size_t csz;
  ssize_t rsz;
  
  if(bp) {
    bl -= bp;
    if(bl) bcopy(buf+bp, buf, bl);
    bp = 0;
  }
  if(eof && !bl) return NULL;
  *p_ln = ln;
  while(1) {
    if(!eof) {
      if(bl==bs) {
        bs += 50 + bs/3;
        if(bs<=bl) { fprintf(stderr, "line %llu too long // out of memory\n", ln); exit(-1); }
        if(!buf) buf = malloc(bs); else buf = realloc(buf, bs);
        if(!buf) { fprintf(stderr, "line %llu too long // out of memory\n", ln); exit(-1); }
      }
      csz = bs-bl;
      if(((ssize_t)csz)<=0) csz/=2;
      while((rsz = read(0, buf+bl, csz))<0) if(errno!=EINTR) { fprintf(stderr, "error reading input at line %llu, error %d (%s)\n", ln, errno, strerror(errno)); rsz = 0; break; }
      if(!rsz) eof = 1; else bl += rsz;
    }
    for( ; bp<bl; bp++) {
      if(buf[bp]!='\n') continue;
      ln++;
      if(!bp) { buf[bp++] = 0; *eoln_type = "\n"; return buf; }
      if(buf[bp-1]=='\\') continue;
      if(buf[bp-1]!='\r') { buf[bp++] = 0; *eoln_type = "\n"; return buf; }
      if(bp==1 || buf[bp-2]!='\\') { buf[bp-1] = 0; bp++; *eoln_type = "\r\n"; return buf; }
    }
    if(eof) {
      assert(bl<bs); /* eof results from failed read() so bs-bl>0 */
      buf[bp] = 0; *eoln_type = NULL; return buf;
    }
  }
}

static void handle_line(char *b, char const *eoln, char const *def_eoln, char *pq, unsigned long ln, int warnq);

int main(int argc, char const * const * argv) {
  char q;
  unsigned long long ln;
  int warnq;
  char *b, *p;
  char const *eoln, *def_eoln;
  
  warnq = !(argc>=2 && !strcmp(argv[1],"--multistring"));
  def_eoln = "\n";
  q = 0;
  while(b=wise_gets(&eoln,&ln)) {
    if(eoln) def_eoln = eoln; else eoln = "";
    handle_line(b, eoln, def_eoln, &q, ln, warnq);
  }
  if(q=='/') fprintf(stderr, "warning: unterminated multiline comment at EOF (last line is %lu)\n", ln);
  else if(q) fprintf(stderr, "warning: unterminated quoted (%c) entity at EOF (last line is %lu)\n", q, ln);
  return 0;
}

static char * skip_eolns(char * b) {
  while(*b=='\\') {
    if(b[1]=='\n') { b+=2; continue; }
    if(b[1]=='\r' && b[2]=='\n') { b+=3; continue; }
    break;
  }
  return b;
}

static void handle_line(char *b, char const *eoln, char const *def_eoln, char *pq, unsigned long ln, int warnq) {
  size_t p, plen;
  char c, q;
  char q0;
  char *bb;
  
  for(p=0; (c=b[p])==' ' || c=='\t'; p++);
  plen = p;
  q = q0 = *pq;
  while(c = b[p]) {
    if(q=='/') {
      p++;
      if(c=='*' && *(bb=skip_eolns(b+p))=='/') { p = (bb-b)+1; q = 0; }
      continue;
    }
    if(q) {
      p++;
      if(c==q) q=0;
      else if(c=='\\') { if(b[p]) p++; }
      continue;
    }
    if(c=='\'' || c=='"') { q=c; p++; continue; }
    if(c=='/' && *(bb=skip_eolns(b+p+1))=='*') { q='/'; p=(bb-b)+1; continue; }
    if(c!='/' || *(bb=skip_eolns(b+p+1))!='/') { p++; continue; }
    /* found unquoted // */
    if(q0) {
      if(q0=='/') fprintf(stderr, "warning: can't safely reorder //-comment due to pending multiline-comment at line %lu beginning\n", ln);
      else fprintf(stderr, "warning: can't safely reorder //-comment due to pending quoted (%c) entity at line %lu beginning\n", q, ln);
      break;
    }
    /* here q0==0 && q==0 */
    if(plen) fwrite(b, 1, plen, stdout);
    fputs(b+p, stdout);
    fputs(def_eoln, stdout);
    while(p && (b[p-1]==' ' || b[p-1]=='\t')) p--;
    if(p) { fwrite(b, 1, p, stdout); fputs(eoln, stdout); }
    return;
  }
  /* found EOLN w/o // */
  fputs(b, stdout); fputs(eoln, stdout);
  *pq = q;
  if(warnq && q && q!='/') fprintf(stderr, "warning: unterminated quoted (%c) entity at line %lu\n", q, ln);
}

PS > gc file.old

code1 // comment1
code2
code3

code4
code5 // comment5
code6

code7
code8 // comment8

PS > & {
   >>    (gc file.old).foreach({
   >>
   >>        if ($_ -match '^.+//')
   >>            { "{1}`n{0}" -f ($_ -split '(?<=^.+\s+)(?=//.+$)') }
   >>        else
   >>            { $_ }
   >>     }) | sc file.new     # sc псевдоним (alias) для Set-Content
   >>  }

PS > gc file.new

// comment1
code1
code2
code3

code4
// comment5
code5
code6

code7
// comment8
code8

sed -i '/^\s*[^[:space:]].*\/\//s:^\([[:space:]]*\)\(.*\)\(\/\/.*\)$:\1\3\n\1\2:'

  //
  /

  // here
  printf("some\" // literal"); // comment

  ///

  // literal"); // comment // here
  printf("some\"