fclose: close stream even if there is an error flushing buffered data.

This can happen, e.g., if there is an IO error or if there is insufficient free disk space to flush the data. In this case, fclose should return -1 to report an error, but it should still effectively close the stream and deallocate the buffer for it. (This behavior is explicitly specified in the C99 and later standards.)

Previously, ORCA/C effectively left the stream open in these cases. As a result, the buffer was not deallocated. More importantly, this could cause the program to hang at exit, because the stream would never be removed from the list of open files.

Here is an example program that demonstrates the problem:

/*
 * Run this on a volume with less than 1MB of free space, e.g. a floppy.
 * The fclose return value should be -1 (EOF), indicating an error, but
 * the two RealFreeMem values should be close to each other (indicating
 * that the buffer was freed), and the program should not hang on exit.
 */

#include <stdio.h>
#include <stddef.h>
#include <memory.h>

#define BUFFER_SIZE 1000000

int main(void) {
        size_t i;
        int ret;

        printf("At start, RealFreeMem = %lu\n", RealFreeMem());

        FILE *f = fopen("testfile", "wb");
        if (!f)
                return 0;

        setvbuf(f, NULL, _IOFBF, BUFFER_SIZE);

        for (i = 0; i < BUFFER_SIZE; i++) {
                putc('x', f);
        }

        ret = fclose(f);
        printf("fclose return value = %d\n", ret);

        printf("At end, RealFreeMem = %lu (should be close to start value)\n",
                RealFreeMem());
}

stdio.asm

@@ -83,16 +83,13 @@ stdfile  equ   7                        is this a standard file?
          phk
          plb
 
-         lda   #EOF                     assume we will get an error
-         sta   err
          ph4   <stream                  verify that stream exists
          jsl   ~VerifyStream
-         jcs   rts
+         jcs   rts_err
 
          ph4   <stream                  do any pending I/O
          jsl   fflush
-         tax
+         sta   err                      initialize err to fflush result
-         jne   rts
 
          stz   stdfile                  not a standard file
          lda   stream+2                 bypass file disposal if the file is
@@ -113,7 +110,7 @@ cl0      lla   p,stderr+4               find the file record that points to this
 cl1      lda   [p],Y
          tax
          ora   [p]
-         jeq   rts
+         jeq   rts_err
          lda   [p]
          cmp   stream
          bne   cl2
@@ -188,7 +185,10 @@ cl6      lda   [p],Y
          dey
          cpy   #2
          bne   cl6
-cl7      stz   err                      no error found
+cl7      bra   rts                      no error found
+
+rts_err  lda   #EOF
+         sta   err
 rts      plb
          creturn   2:err