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Fix reading files larger than 2GiB on macOS #3

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Fix reading files larger than 2GiB on macOS #3

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ff39f61
Fix silent read failure in load(): use perror and exit instead of pai…
Apr 13, 2026
f6bdbd0
Limit read() to 0x7FFF0000 bytes per call to fix >2GiB files on macOS
Apr 13, 2026
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17 changes: 12 additions & 5 deletions io.c
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Original file line number Diff line number Diff line change
Expand Up @@ -58,13 +58,17 @@
#endif


//@ read on linux has a limit of 0x7ffff000 bytes (see `man read`)
//@ this function calls recursively read until all `count` characters are read.
//@ linux read() clamps to 0x7ffff000 bytes per call (see `man read`)
//@ macOS read() returns EINVAL if count > INT_MAX (0x7fffffff)
//@ cap each read and loop until all `count` bytes are read.
#define READ_MAX 0x7FFF0000
static ssize_t
read_to_end(int fd, void *buf, size_t count) {
size_t read_bytes = 0;
while(read_bytes < count) {
const ssize_t ret = read(fd, ((char*)buf)+read_bytes, count-read_bytes);
size_t remaining = count - read_bytes;
if(remaining > READ_MAX) remaining = READ_MAX;
const ssize_t ret = read(fd, ((char*)buf)+read_bytes, remaining);
if(ret <= 0) return ret;
read_bytes += ret;
}
Expand Down Expand Up @@ -290,8 +294,11 @@ load(char *fname)
} else if ((filemode == REGULAR) || (filemode == DIRECTORY)) {
filesize = buf.st_size;
if (read_to_end(fd, mem, filesize) != filesize) {
sysemsg(fname);
filemode = ERROR;
close(fd);
move(maxy, 0);
endwin();
perror(fname);
exit(0);
}
} else {
filesize = 0L;
Expand Down