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tempfile: avoid "ferror | fclose" trick
The current code wants to record an error condition from either ferror() or fclose(), but makes sure that we always call both functions. So it can't use logical-OR "||", which would short-circuit when ferror() is true. Instead, it uses bitwise-OR "|" to evaluate both functions and set one or more bits in the "err" flag if they reported a failure. Unlike logical-OR, though, bitwise-OR does not introduce a sequence point, and the order of evaluation for its operands is unspecified. So a compiler would be free to generate code which calls fclose() first, and then ferror() on the now-freed filehandle. There's no indication that this has happened in practice, but let's write it out in a way that follows the standard. Noticed-by: Andreas Schwab <schwab@linux-m68k.org> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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@ -247,12 +247,8 @@ int close_tempfile(struct tempfile *tempfile)
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tempfile->fd = -1;
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tempfile->fd = -1;
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if (fp) {
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if (fp) {
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tempfile->fp = NULL;
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tempfile->fp = NULL;
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err = ferror(fp);
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/*
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err |= fclose(fp);
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* Note: no short-circuiting here; we want to fclose()
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* in any case!
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*/
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err = ferror(fp) | fclose(fp);
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} else {
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} else {
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err = close(fd);
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err = close(fd);
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}
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}
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