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C Programming
Table of "safe" methods to suppress "unused parameter" warnings?
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<blockquote data-quote="mathog" data-source="post: 5151576"><p>Here is a small example program to test these methods on</p><p>various compilers. The results I found follow the program.</p><p>(I don't have access to all that many compilers, and some of them are</p><p>very old.)</p><p></p><p>---cut here -- test_unused.c --</p><p>#include <stdlib.h></p><p>#include <stdio.h></p><p></p><p>#ifdef UNUSED</p><p>#elif defined(__GNUC__)</p><p># define UNUSED(x) UNUSED_ ## x __attribute__((unused))</p><p>#elif defined(__LCLINT__)</p><p># define UNUSED(x) /*@unused@*/ x</p><p>#else</p><p># define UNUSED(x) x</p><p>#endif</p><p></p><p></p><p>void method1(int x){</p><p>(void) x;</p><p>printf("method 1\n");</p><p>}</p><p></p><p>void method2(int x){</p><p>x = x;</p><p>printf("method 2\n");</p><p>}</p><p></p><p>void method3(int x){</p><p>*(volatile typeof(x) *) &(x) = (x);</p><p>printf("method 3\n");</p><p>}</p><p></p><p>void method4(int x){</p><p>if(x){};</p><p>printf("method 4\n");</p><p>}</p><p></p><p>void method5(int UNUSED(x)){</p><p>printf("method 5\n");</p><p>}</p><p></p><p>int main(void){</p><p>method1(1);</p><p>method2(1);</p><p>method3(1);</p><p>method4(1);</p><p>method5(1);</p><p>exit(EXIT_SUCCESS);</p><p>}</p><p>---cut here ----</p><p></p><p>Results:</p><p></p><p>(gcc 4.6.3 and 4.7.2 tested, they did the same thing)</p><p>gcc -Wall -Wextra --std=c99 -o test_unused test_unused.c</p><p>warns:</p><p>test_unused.c: In function 'method3':</p><p>test_unused.c:24:4: error: unknown type name 'typeof'</p><p>test_unused.c:24:22: error: expected ')' before 'x'</p><p>test_unused.c:24:25: error: expected ')' before '*' token</p><p></p><p>gcc -Wall -Wextra -o test_unused test_unused.c</p><p>no warnings</p><p></p><p>(Ubuntu clang version 3.0-6ubuntu3 (tags/RELEASE_30/final) (based on</p><p>LLVM 3.0))</p><p>clang -Wall -o test_unused test_unused.c</p><p>warns:</p><p>test_unused.c:20:6: warning: explicitly assigning a variable</p><p>of type 'int' to itself [-Wself-assign]</p><p>x = x;</p><p>~ ^ ~</p><p></p><p>(A very old version of the intel linux compiler == 9.0)</p><p>iccbin -Wall -std=c99 -gcc-version=340 -i-static \</p><p>-o test_unused test_unused.c</p><p>warns about "external definition with no prior declaration" for all</p><p>of the functions, but did not warn about anything else.</p><p></p><p>(A very old version of the Sun Forte Developer 7.0 C 5.4</p><p>on an equally old Sparc)</p><p>cc -o test_unused test_unused.c</p><p>warns:</p><p>"test_unused.c", line 25: warning: no explicit type given</p><p>"test_unused.c", line 25: syntax error before or at: typeof</p><p>"test_unused.c", line 29: type specifier can not be used as array size</p><p>expression qualifier</p><p>"test_unused.c", line 29: warning: no explicit type given</p><p>"test_unused.c", line 29: cannot recover from previous errors</p><p></p><p>And that's all the compilers I have to test.</p><p></p><p></p><p>Regards,</p><p></p><p>David Mathog</p></blockquote><p></p>
[QUOTE="mathog, post: 5151576"] Here is a small example program to test these methods on various compilers. The results I found follow the program. (I don't have access to all that many compilers, and some of them are very old.) ---cut here -- test_unused.c -- #include <stdlib.h> #include <stdio.h> #ifdef UNUSED #elif defined(__GNUC__) # define UNUSED(x) UNUSED_ ## x __attribute__((unused)) #elif defined(__LCLINT__) # define UNUSED(x) /*@unused@*/ x #else # define UNUSED(x) x #endif void method1(int x){ (void) x; printf("method 1\n"); } void method2(int x){ x = x; printf("method 2\n"); } void method3(int x){ *(volatile typeof(x) *) &(x) = (x); printf("method 3\n"); } void method4(int x){ if(x){}; printf("method 4\n"); } void method5(int UNUSED(x)){ printf("method 5\n"); } int main(void){ method1(1); method2(1); method3(1); method4(1); method5(1); exit(EXIT_SUCCESS); } ---cut here ---- Results: (gcc 4.6.3 and 4.7.2 tested, they did the same thing) gcc -Wall -Wextra --std=c99 -o test_unused test_unused.c warns: test_unused.c: In function 'method3': test_unused.c:24:4: error: unknown type name 'typeof' test_unused.c:24:22: error: expected ')' before 'x' test_unused.c:24:25: error: expected ')' before '*' token gcc -Wall -Wextra -o test_unused test_unused.c no warnings (Ubuntu clang version 3.0-6ubuntu3 (tags/RELEASE_30/final) (based on LLVM 3.0)) clang -Wall -o test_unused test_unused.c warns: test_unused.c:20:6: warning: explicitly assigning a variable of type 'int' to itself [-Wself-assign] x = x; ~ ^ ~ (A very old version of the intel linux compiler == 9.0) iccbin -Wall -std=c99 -gcc-version=340 -i-static \ -o test_unused test_unused.c warns about "external definition with no prior declaration" for all of the functions, but did not warn about anything else. (A very old version of the Sun Forte Developer 7.0 C 5.4 on an equally old Sparc) cc -o test_unused test_unused.c warns: "test_unused.c", line 25: warning: no explicit type given "test_unused.c", line 25: syntax error before or at: typeof "test_unused.c", line 29: type specifier can not be used as array size expression qualifier "test_unused.c", line 29: warning: no explicit type given "test_unused.c", line 29: cannot recover from previous errors And that's all the compilers I have to test. Regards, David Mathog [/QUOTE]
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Table of "safe" methods to suppress "unused parameter" warnings?
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