forked from Mirrors/tinycc
123 lines
2.6 KiB
C
123 lines
2.6 KiB
C
/* This checks various ways of dead code inside if statements
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where there are non-obvious ways of how the code is actually
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not dead due to reachable by labels. */
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extern int printf (const char *, ...);
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static void kb_wait_1(void)
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{
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unsigned long timeout = 2;
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do {
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/* Here the else arm is a statement expression that's supposed
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to be suppressed. The label inside the while would unsuppress
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code generation again if not handled correctly. And that
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would wreak havoc to the cond-expression because there's no
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jump-around emitted, the whole statement expression really
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needs to not generate code (perhaps except useless forward jumps). */
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(1 ?
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printf("timeout=%ld\n", timeout) :
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({
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int i = 1;
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while (1)
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while (i--)
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some_label:
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printf("error\n");
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goto some_label;
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})
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);
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timeout--;
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} while (timeout);
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}
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int main (void)
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{
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int i = 1;
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kb_wait_1();
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/* Simple test of dead code at first sight which isn't actually dead. */
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if (0) {
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yeah:
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printf ("yeah\n");
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} else {
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printf ("boo\n");
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}
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if (i--)
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goto yeah;
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/* Some more non-obvious uses where the problems are loops, so that even
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the first loop statements aren't actually dead. */
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i = 1;
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if (0) {
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while (i--) {
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printf ("once\n");
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enterloop:
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printf ("twice\n");
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}
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}
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if (i >= 0)
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goto enterloop;
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/* The same with statement expressions. One might be tempted to
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handle them specially by counting if inside statement exprs and
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not unsuppressing code at loops at all then.
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See kb_wait_1 for the other side of the medal where that wouldn't work. */
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i = ({
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int j = 1;
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if (0) {
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while (j--) {
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printf ("SEonce\n");
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enterexprloop:
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printf ("SEtwice\n");
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}
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}
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if (j >= 0)
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goto enterexprloop;
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j; });
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/* The other two loop forms: */
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i = 1;
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if (0) {
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for (i = 1; i--;) {
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printf ("once2\n");
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enterloop2:
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printf ("twice2\n");
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}
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}
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if (i > 0)
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goto enterloop2;
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i = 1;
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if (0) {
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do {
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printf ("once3\n");
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enterloop3:
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printf ("twice3\n");
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} while (i--);
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}
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if (i > 0)
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goto enterloop3;
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/* And check that case and default labels have the same effect
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of disabling code suppression. */
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i = 41;
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switch (i) {
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if (0) {
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printf ("error\n");
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case 42:
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printf ("error2\n");
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case 41:
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printf ("caseok\n");
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}
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}
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i = 41;
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switch (i) {
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if (0) {
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printf ("error3\n");
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default:
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printf ("caseok2\n");
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break;
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case 42:
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printf ("error4\n");
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}
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}
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return 0;
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}
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