From: Tom Jones Subject: diff: Don't return errno when fread fails To: gameoftrees@openbsd.org Date: Tue, 11 Oct 2022 09:42:26 +0100 fread doesn't consistently set errno on failure. - On OpenBSD fread sets errno on possible argument overflows, but this doesn't occur on other platforms. rfread doesn't set errno on EOF or other failures. - ferror does not set errno on failure. Returning errno here is possibly inconsistent. Return EIO here instead. - Tom diff --git a/lib/diff_atomize_text.c b/lib/diff_atomize_text.c index dd6b2aa..238ecb9 100644 --- a/lib/diff_atomize_text.c +++ b/lib/diff_atomize_text.c @@ -64,7 +64,7 @@ diff_data_atomize_text_lines_fd(struct diff_data *d) while (eol == 0 && line_end < end) { r = fread(buf, sizeof(char), sizeof(buf), d->root->f); if (r == 0 && ferror(d->root->f)) - return errno; + return EIO; i = 0; while (eol == 0 && i < r) { if (buf[i] != '\r' && buf[i] != '\n') { @@ -91,7 +91,7 @@ diff_data_atomize_text_lines_fd(struct diff_data *d) return errno; r = fread(buf, sizeof(char), sizeof(buf), d->root->f); if (r == 0 && ferror(d->root->f)) - return errno; + return EIO; if (r > 0 && buf[0] == '\n') line_end++; } diff --git a/lib/diff_main.c b/lib/diff_main.c index 3043a9d..32c3dac 100644 --- a/lib/diff_main.c +++ b/lib/diff_main.c @@ -43,7 +43,7 @@ read_at(FILE *f, off_t at_pos, unsigned char *buf, size_t len) return errno; r = fread(buf, sizeof(char), len, f); if ((r == 0 || r < len) && ferror(f)) - return errno; + return EIO; if (r != len) return EIO; return 0;