Switching focus back to vim buffer populates macros from included headers

[Uday Reddy B]

Hello,

I've suddenly run into a situation where bringing the focus back to the vim buffer is making vim, YCM, or something else populate the whole list of macros from included header files related to the word under the cursor (as shown below). I don't recall changing anything in my YCM conf/.vimrc. I'm using YCM at 49ced5a30ad7778178fd44703665a8ef3329e592 with vim 8.1 (Ubuntu 22.04). I do recall running into this a year or two ago, but can't recall what the culprit was. It happens when one switches focus out of the terminal tab or the window and then comes back to this buffer. All relevant declarations in header files included appear to be listed out in a new buffer that has to be exited to get back to the buffer being edited. 

Example:

/usr/include/math.h
  4:    8    version 2.1 of the License, or (at your option) any later version.
  5:   24 #define _MATH_H 1
/usr/include/bits/libc-header-start.h
  6:    8    version 2.1 of the License, or (at your option) any later version.
/usr/include/features.h
  7:    7    version 2.1 of the License, or (at your option) any later version.
  8:   19 #define _FEATURES_H 1
  9:   31       Extensions to ISO C11 from TS 18661-1:2014.
 10:   37    _POSIX_SOURCE  IEEE Std 1003.1.
 11:   38    _POSIX_C_SOURCE  If ==1, like _POSIX_SOURCE; if >=2 add IEEE Std 1003.2;
 12:   41       if >=200112L, all of IEEE 1003.1-2004
 13:   42       if >=200809L, all of IEEE 1003.1-2008
 14:   56       Set to 1 or 2; 2 performs stricter checks than 1.
 15:   68    give you ISO C, 1003.1, and 1003.2, but nothing else.
 16:   74       to 1 or 0; the subsequent macros are either defined
 17:   81    __USE_POSIX    Define IEEE Std 1003.1 things.
 18:   83    __USE_POSIX199309  Define IEEE Std 1003.1, and .1b things.
 19:   84    __USE_POSIX199506  Define IEEE Std 1003.1, .1b, .1c and .1i things.
 20:  189 # define _DEFAULT_SOURCE  1
 21:  195 # define _ISOC95_SOURCE 1
 22:  197 # define _ISOC99_SOURCE 1
 23:  199 # define _ISOC11_SOURCE 1
 24:  201 # define _ISOC2X_SOURCE 1
 25:  203 # define _POSIX_SOURCE  1
 26:  209 # define _XOPEN_SOURCE_EXTENDED 1
 27:  211 # define _LARGEFILE64_SOURCE  1
 28:  213 # define _DEFAULT_SOURCE  1
 29:  215 # define _ATFILE_SOURCE 1
 30:  227 # define _DEFAULT_SOURCE  1
 31:  233 # define __GLIBC_USE_ISOC2X 1
 32:  241 # define __USE_ISOC11 1
 33:  248 # define __USE_ISOC99 1
 34:  251 /* This is to enable the ISO C90 Amendment 1:1995 extension.  */
 35:  255 # define __USE_ISOC95 1
 36:  261 #  define __USE_ISOC11  1
 37:  266 #  define __USE_ISOCXX11  1
 38:  267 #  define __USE_ISOC99  1
 39:  272    is defined, use POSIX.1-2008 (or another version depending on
 40:  276 #  define __USE_POSIX_IMPLICITLY  1
 41:  279 # define _POSIX_SOURCE  1
 42:  287 # define _POSIX_SOURCE  1
 43:  297 # define __USE_POSIX_IMPLICITL