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llvm-project/clang/test/Analysis/flexignore.c

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[analyzer] Ignore flex generated files Some projects [1,2,3] have flex-generated files besides bison-generated ones. Unfortunately, the comment `"/* A lexical scanner generated by flex */"` generated by the tools is not necessarily at the beginning of the file, thus we need to quickly skim through the file for this needle string. Luckily, StringRef can do this operation in an efficient way. That being said, now the bison comment is not required to be at the very beginning of the file. This allows us to detect a couple more cases [4,5,6]. Alternatively, we could say that we only allow whitespace characters before matching the bison/flex header comment. That would prevent the (probably) unnecessary string search in the buffer. However, I could not verify that these tools would actually respect this assumption. Additionally to this, e.g. the Twin project [1] has other non-whitespace characters (some preprocessor directives) before the flex-generated header comment. So the heuristic in the previous paragraph won't work with that. Thus, I would advocate the current implementation. According to my measurement, this patch won't introduce measurable performance degradation, even though we will do 2 linear scans. I introduce the ignore-bison-generated-files and ignore-flex-generated-files to disable skipping these files. Both of these options are true by default. [1]: https://github.com/cosmos72/twin/blob/master/server/rcparse_lex.cpp#L7 [2]: https://github.com/marcauresoar/make-examples/blob/22362cdcf9dd7c597b5049ce7f176621e2e9ac7a/sandbox/count-words/lexer.c#L6 [3]: https://github.com/vladcmanea/2nd-faculty-year-Formal-Languages---Automata-assignments/blob/11abdf64629d9eb741438ba69f04636769d5a374/lab1/lex.yy.c#L6 [4]: https://github.com/KritikaChoudhary/System-Software-Lab/blob/47f5b2cfe2a2738fd54eae9f8439817f6a22034e/B_yacc/1/y1.tab.h#L2 [5]: https://github.com/VirtualMonitor/VirtualMonitor/blob/71d1bf9b1e7b392a7bd0c73dc217138dc5865651/src/VBox/Additions/x11/x11include/xorg-server-1.8.0/parser.h#L2 [6]: https://github.com/bspaulding/DrawTest/blob/3f773ceb13de14275429036b9cbc5aa19e29bab9/Framework/OpenEars.framework/Versions/A/Headers/jsgf_parser.h#L2 Reviewed By: xazax.hun Differential Revision: https://reviews.llvm.org/D114510
2021-12-06 17:20:17 +08:00
// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify -DEXPECT_NO_DIAGNOSTICS %s
// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify=conditional %s \
// RUN: -analyzer-config ignore-flex-generated-files=false
#ifdef EXPECT_NO_DIAGNOSTICS
// expected-no-diagnostics
#endif
/* A lexical scanner generated by flex */
A significant number of our tests in C accidentally use functions without prototypes. This patch converts the function signatures to have a prototype for the situations where the test is not specific to K&R C declarations. e.g., void func(); becomes void func(void); This is the ninth batch of tests being updated (there are a significant number of other tests left to be updated).
2022-02-13 21:02:46 +08:00
void clang_analyzer_warnIfReached(void);
void foo(void) {
[analyzer] Ignore flex generated files Some projects [1,2,3] have flex-generated files besides bison-generated ones. Unfortunately, the comment `"/* A lexical scanner generated by flex */"` generated by the tools is not necessarily at the beginning of the file, thus we need to quickly skim through the file for this needle string. Luckily, StringRef can do this operation in an efficient way. That being said, now the bison comment is not required to be at the very beginning of the file. This allows us to detect a couple more cases [4,5,6]. Alternatively, we could say that we only allow whitespace characters before matching the bison/flex header comment. That would prevent the (probably) unnecessary string search in the buffer. However, I could not verify that these tools would actually respect this assumption. Additionally to this, e.g. the Twin project [1] has other non-whitespace characters (some preprocessor directives) before the flex-generated header comment. So the heuristic in the previous paragraph won't work with that. Thus, I would advocate the current implementation. According to my measurement, this patch won't introduce measurable performance degradation, even though we will do 2 linear scans. I introduce the ignore-bison-generated-files and ignore-flex-generated-files to disable skipping these files. Both of these options are true by default. [1]: https://github.com/cosmos72/twin/blob/master/server/rcparse_lex.cpp#L7 [2]: https://github.com/marcauresoar/make-examples/blob/22362cdcf9dd7c597b5049ce7f176621e2e9ac7a/sandbox/count-words/lexer.c#L6 [3]: https://github.com/vladcmanea/2nd-faculty-year-Formal-Languages---Automata-assignments/blob/11abdf64629d9eb741438ba69f04636769d5a374/lab1/lex.yy.c#L6 [4]: https://github.com/KritikaChoudhary/System-Software-Lab/blob/47f5b2cfe2a2738fd54eae9f8439817f6a22034e/B_yacc/1/y1.tab.h#L2 [5]: https://github.com/VirtualMonitor/VirtualMonitor/blob/71d1bf9b1e7b392a7bd0c73dc217138dc5865651/src/VBox/Additions/x11/x11include/xorg-server-1.8.0/parser.h#L2 [6]: https://github.com/bspaulding/DrawTest/blob/3f773ceb13de14275429036b9cbc5aa19e29bab9/Framework/OpenEars.framework/Versions/A/Headers/jsgf_parser.h#L2 Reviewed By: xazax.hun Differential Revision: https://reviews.llvm.org/D114510
2021-12-06 17:20:17 +08:00
clang_analyzer_warnIfReached(); // conditional-warning {{REACHABLE}}
}