Fix #958: warn when feof() is used as a while loop condition#8422
Fix #958: warn when feof() is used as a while loop condition#8422francois-berder wants to merge 5 commits intodanmar:mainfrom
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feof() only returns true after a read has already failed, causing the loop body to execute once more after the last successful read. Read errors also go undetected since feof() does not distinguish them from EOF. Signed-off-by: Francois Berder <fberder@outlook.fr>
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How does the check handle |
lib/checkio.cpp
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| if (!cond) | ||
| continue; |
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this code is redundant. simpleMatch returns false if the token is null
| if (!cond) | |
| continue; |
lib/checkio.cpp
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| { | ||
| reportError(tok, Severity::warning, | ||
| "wrongfeofUsage", | ||
| "Using feof() as a loop condition may cause the last line to be processed twice.\n" |
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I want that you remove the word "may". Can you somehow check if it is actually processed twice.
if there is no bug we shouldn't warn. example:
char line[100];
fgets(line, sizeof(line), f);
while (!feof(f)) {
dostuff(line);
fgets(line, sizeof(line), f);
}
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I improved this check by looking for a file read call before the loop and within the loop. This should cover this case but I am aware that it will lead to some FP/FN (cause by break statements in the loop body).
test/testio.cpp
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| void testWrongfeofUsage() { // ticket #958 | ||
| check("void foo() {\n" | ||
| " FILE * fp = fopen(\"test.txt\", \"r\");\n" |
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You can pass fp as parameter. then the testcase can be 2 lines shorter (no open/close).
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thank you for adding this checker! it's good work. small and simple. just try to make it more precise. |
…ile loop condition
…as a while loop condition
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3 participants
feof() only returns true after a read has already failed, causing the loop body to execute once more after the last successful read. Read errors also go undetected since feof() does not distinguish them from EOF.