Add missing format parsing

[fnadeau]

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Node : 6.5.0

Requirements

Highlight of format specifier.

Small test that can be use for regression

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

int main ()
{
  // http://man7.org/linux/man-pages/man3/scanf.3.html
  // http://man7.org/linux/man-pages/man3/printf.3.html
  int int1, int2;
  char *str1 = NULL;
  char str2[32];
  // Field argument
  sscanf("10 20", "%2$d %1$d", &int2, &int1);
  printf("%2$*1$d\n", int1, int2); // output: "        20"
  // flags
  printf("%.*d|%#04X|%-5d|% 3d\n",
         5, int1, int2, 0x1EE1, 0xE11E); // output: "00010|0X14|7905 | 57630"
  // Only works if locale uses a char as radix character
  printf("%'.2f\n", 1234567.89);
  //width & precision
  printf( "|%-5d|%5d|\n", 1, 2);              // output: "|1    |    2|"
  printf( "|%1$*2$d|\n", 5, 3);               // output: "|  5|"
  printf("%5.2f\n", 6.28318530718);           // output: " 6.28"
  printf("%.8f\n", 1.61803398875);            // output: "1.61803399"
  printf("%1$*2$.*3$f\n", 1234567.89, 12, 1); // output: "   1234567.9"
  //length modifier
  printf("%1$hhd|%1$hd|%1$d\n", 0x2000100A);  // output: "10|4106|536875018"
  sscanf("discard:value", "%*[a-z]:%ms", &str1);
  printf( "%s\n", str1 );                     // output: "value"
  free(str1);
  str1 = NULL;

  // Bug, should not highligh the 's'
  // %ms is a valid scanf, major rewrite will be needed to fix that corner case
  printf("%ms\n"); // print value of strerror(errno) followed by s: "Successs"

  sscanf("discard]:value", "%*[^]0-9-]]:%s", str2);
  printf( "%s\n", str2 ); // output: "value"

  sscanf("discard]:value", "%m[]drcasi]:%s", &str1, str2);
  printf( "%s|%s\n", str1, str2 ); // output: "discard]|value"
  free(str1);
  str1 = NULL;

  // Should %d be highlighed here? I think not. Major rewrite required.
  puts("this is not a formated place holder %d");

  printf("%%good\n");
  //these compiles with warning but are not good practice
  printf("%#04%\n");
  printf("%wrong\n");

  return 0;
}

Description of the Change

Current implementation does not deal properly with the following:

printf format:

• %m will print strerror(errno)

for scanf format:

• optional 'm' can be used with string conversions
• [ is a valid conversion specifier

literal %:

• do not match when literal % is used with other flags

Alternate Designs

The parser could be re-written to distinguish between quoted format specifier string and quoted string. It could also distinguish between scanf and printf in order to deal with %m parsing.

The proposed solution was kept for simplicity reason.

Benefits

Proper highlight of valide format specifier

Possible Drawbacks

None

Applicable Issues

The following is not be hilighted properly:
printf("%ms");
the 's' it not part of the conversion specifier in
this case but is when used with scanf.

[fnadeau]

Who's doing the review?

[winstliu]

shouldn't this be a single %?

[fnadeau]

No, you'll end up with this (line 48):

because of the | (or) on line 715, you need two '%'. Previously, the literal '%' was match using two: first on line 707 and second one on line 714.

[winstliu]

Ah, I missed the |. Thanks for explaining.

[winstliu]

Can you please add some specs that cover these changes?

[sean-mcmanus]

What's the status of this? Someone requested this at microsoft/vscode-cpptools#1149 , so that '%[' works in fscanf.

[winstliu]

As per my last comment, it still needs specs to be considered.

[fnadeau]

I update the function so that it's a bit more easy to read/review

Spec:
printf: http://pubs.opengroup.org/onlinepubs/9699919799/functions/printf.html
scanf: http://pubs.opengroup.org/onlinepubs/9699919799/functions/scanf.html

Linux:
http://man7.org/linux/man-pages/man3/printf.3.html
http://man7.org/linux/man-pages/man3/scanf.3.html

Nice formatted tables (incomplete though):
http://www.cplusplus.com/reference/cstdio/scanf/
http://www.cplusplus.com/reference/cstdio/printf/

New screenshot