[gccsdk] Unexpected results with fseek() and SEEK_CUR

If the file qqq contains the single line:
abcdefghijklmnopq

then on Cygwin the following program gives what I would expect:
abcdefghijklmnopq
abcdefghi
abcdEfghijklmnopq

but on RISC OS gcc 4.7.4, VirtualRPC-Adjust RISCOS 4.39, ARM 710, the
last output line is wrong:
abcdefghijklmnopq
abcdefghi
abcdefghijklmEopq

RISC OS seems to be using SEEK_END instead of SEEK_CUR.
Is this a bug in RISC OS gcc, or is it something that just can't be done
on RISC OS?

#include <stdio.h>

int main(void) {
int i;
FILE* fp=fopen("qqq","rb+");

while ((i=fgetc(fp))!=EOF)
printf("%c",i);

if (fseek(fp,0,SEEK_SET)) {
printf("fseek() error 1\n");
return 1;
}
for(i=0;i<9;++i)
printf("%c",fgetc(fp));
printf("\n");

if (fseek(fp,-5,SEEK_CUR)) {
printf("fseek() error 2\n");
return 1;
}
fputc((int) 'E',fp);

if (fseek(fp,0,SEEK_SET)) {
printf("fseek() error 3\n");
return 1;
}
while ((i=fgetc(fp))!=EOF)
printf("%c",i);

fclose(fp);

return 0;
}

Regards, Duncan

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