Le 19/10/2015 16:09, Rainer Weikusat a écrit :
Edward Bartolo <[email protected]> writes:
Could someone explain to me what is the meaning of this error and what
I should do to avoid having this warning?
edbarx@edbarx-pc:~/netman/backend_src/src$ gcc -Wall -Wfatal-errors -g
-lm -I../include core_functions.c file_functions.c backend.c
essid_encoder.c automated_scanner.c -o backend
automated_scanner.c: In function ‘autoWirelessScanPlus_RN’:
automated_scanner.c:521:2: warning: suggest parentheses around
assignment used as truth value [-Wparentheses]
if ( dir = opendir(IFACES_PATH) ) {
^
The warning really only communicates that - ca 42 years ago - some
... American (!!1) dared to do something Nikolaus Wirth strongly
disapproved of, namely, make assignment an expression instead of a
statement (something Mr Wirth already strongly(!!2) disapproved of the
the context of Algo 68) and then didn't use the assignment operator Mr
Wirth had approved of (!!3), namely, :=.
I don't know if this is the oldest, entirely pointless "programming
language syntax war" in existance but it's surely one of the most
persistently annoying ones[*].
[*] Sometimes, when noticing that everyone else is driving in the
opposite direction on a motorway, you're actually wrong yourself ...
Writing "if (a = b)" when meaning "if (a == b)" is a very easy
mistake. Yes it is dangerous, because difficult to notice and it changes
dramatically the behaviour of the program. Any C programmer pretending
to never have made this mistake is a liar. Gcc authors have aknowledged
the fact by introducing this parenthesis feature which is supposed to
mean "yes I do mean an assignment".
You are right, C cumulates these two features:
1) the assignment operator is '='
2) the assignment is an expression.
Sure both are motivated; but the motivations are mostly aesthetical
while the combination is an unextinguishable source of bugs. I don't
think you can accuse the authors of gcc to make the war against the C
language because they warn you against this possible mistake, or do you
mean this Mr Wirth you seem to disaprove is (one of) the authors of gcc?
Didier
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