Obsolete code, fails to build on modern system.

[EvilGremlin]

[eg@EGDesktop epk2extract-master]$ ./build.sh 
Building epk2extract
-- Configuring done (0.1s)
-- Generating done (0.0s)
-- Build files have been written to: /home/eg/Загрузки/epk2extract-master/build_linux/obj
[  3%] Built target mfile
[  9%] Built target utils
[ 13%] Built target stream
[ 18%] Built target cramfs
[ 38%] Built target squashfs
[ 44%] Built target lz4
[ 50%] Built target lzma
[ 56%] Built target jffs2
[ 61%] Built target lzhs
[ 63%] Building C object src/CMakeFiles/epk2extract.dir/minigzip.c.o
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:350:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C23
      [-Wdeprecated-non-prototype]
  350 | void error(msg)
      |      ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:354:5: error: call to undeclared library function 'exit' with type 'void (int) __attribute__((noreturn))'; ISO C99 and later do
      not support implicit function declarations [-Wimplicit-function-declaration]
  354 |     exit(1);
      |     ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:354:5: note: include the header <stdlib.h> or explicitly provide a declaration for 'exit'
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:361:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C23
      [-Wdeprecated-non-prototype]
  361 | void gz_compress(in, out)
      |      ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:394:5: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C23
      [-Wdeprecated-non-prototype]
  394 | int gz_compress_mmap(in, out)
      |     ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:429:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C23
      [-Wdeprecated-non-prototype]
  429 | void gz_uncompress(in, out)
      |      ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:456:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C23
      [-Wdeprecated-non-prototype]
  456 | void file_compress(file, mode)
      |      ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:464:9: error: call to undeclared library function 'strlen' with type 'unsigned long (const char *)'; ISO C99 and later do not
      support implicit function declarations [-Wimplicit-function-declaration]
  464 |     if (strlen(file) + strlen(GZ_SUFFIX) >= sizeof(outfile)) {
      |         ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:464:9: note: include the header <string.h> or explicitly provide a declaration for 'strlen'
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:495:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C23
      [-Wdeprecated-non-prototype]
  495 | void file_uncompress(file)
      |      ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:515:29: error: call to undeclared library function 'strcmp' with type 'int (const char *, const char *)'; ISO C99 and later do
      not support implicit function declarations [-Wimplicit-function-declaration]
  515 |     if (len > SUFFIX_LEN && strcmp(file+len-SUFFIX_LEN, GZ_SUFFIX) == 0) {
      |                             ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:515:29: note: include the header <string.h> or explicitly provide a declaration for 'strcmp'
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:561:15: error: call to undeclared library function 'malloc' with type 'void *(unsigned long)'; ISO C99 and later do not support
      implicit function declarations [-Wimplicit-function-declaration]
  561 |         char *dest = malloc(len + strlen(path));        //allocate space for path+name
      |                      ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:561:15: note: include the header <stdlib.h> or explicitly provide a declaration for 'malloc'
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:562:2: error: call to undeclared library function 'memset' with type 'void *(void *, int, unsigned long)'; ISO C99 and later do
      not support implicit function declarations [-Wimplicit-function-declaration]
  562 |         memset(dest, 0x0, strlen(dest));
      |         ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:562:2: note: include the header <string.h> or explicitly provide a declaration for 'memset'
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:569:2: error: call to undeclared library function 'strcat' with type 'char *(char *, const char *)'; ISO C99 and later do not
      support implicit function declarations [-Wimplicit-function-declaration]
  569 |         strcat(dest, path);
      |         ^
/home/eg/Загрузки/epk2extract-master/src/minigzip.c:569:2: note: include the header <string.h> or explicitly provide a declaration for 'strcat'
6 warnings and 6 errors generated.
make[2]: *** [src/CMakeFiles/epk2extract.dir/build.make:233: src/CMakeFiles/epk2extract.dir/minigzip.c.o] Ошибка 1
make[1]: *** [CMakeFiles/Makefile2:379: src/CMakeFiles/epk2extract.dir/all] Ошибка 2
make: *** [Makefile:91: all] Ошибка 2
Build Failed!
[eg@EGDesktop epk2extract-master]$ gcc --version
gcc (GCC) 15.2.0 20250808 (OpenMandriva)

Tweaks needed, at lest set compiler flag for earlier C version.