[libFuzzer] fix missing close on opened file

[pchaigno]

Summary

When running the standalone main on a large corpus, I eventually get a
EMFILE error ("Too many open files").

Patch by Paul Chaignon

[lebedev.ri]

lib/fuzzer/standalone/StandaloneFuzzTargetMain.c

34 ↗

(On Diff #188152)

You probably can even close it right after fread?

[pchaigno]

lib/fuzzer/standalone/StandaloneFuzzTargetMain.c

34 ↗

(On Diff #188152)

Yes. I wasn't sure what was best: closing as soon as possible or grouping the "cleaning actions".

[pchaigno]

Close the file as soon as possible.

[pchaigno]

I do not have the necessary commit access to commit this change myself.

compiler-rt/trunk/lib/fuzzer/standalone/StandaloneFuzzTargetMain.c

for (int i = 1; i < argc; i++) {
     fprintf(stderr, "Running: %s\n", argv[i]);
     FILE *f = fopen(argv[i], "r");
     assert(f);
     fseek(f, 0, SEEK_END);
     size_t len = ftell(f);
     fseek(f, 0, SEEK_SET);
     unsigned char *buf = (unsigned char*)malloc(len);
     size_t n_read = fread(buf, 1, len, f);
+    fclose(f);
     assert(n_read == len);
     LLVMFuzzerTestOneInput(buf, len);
     free(buf);
     fprintf(stderr, "Done:    %s: (%zd bytes)\n", argv[i], n_read);
   }
 }