[H3] Use fuzzers from uber/h3 (#8406)

Use fuzzers from https://github.com/uber/h3/tree/master/src/apps/fuzzers
rather than the built in one. These additional fuzzers should provide
more complete coverage of the library, and should include all functions
currently fuzzed by oss-fuzz.

We can perhaps further clean up the build process to just pass
`$LIB_FUZZING_ENGINE` in to the fuzzers. In the mean time I just built
the fuzzers directly.

projects/h3/Dockerfile

@@ -19,4 +19,4 @@ RUN apt-get update && apt-get install -y make autoconf automake libtool \
   pkg-config
 RUN git clone --depth 1 https://github.com/uber/h3
 WORKDIR h3
-COPY build.sh h3_fuzzer.c $SRC/
+COPY build.sh $SRC/

projects/h3/build.sh

@@ -17,18 +17,25 @@
 
 mkdir build
 cd build
-sed -i '21d' $SRC/h3/CMakeLists.txt
 cmake ..
-make -j$(nproc)
-$CC $CFLAGS -DH3_PREFIX="" \
-    -I/src/h3/src/apps/applib/include \
-    -I/src/h3/src/h3lib/include \
-    -I/src/h3/build/src/h3lib/include \
-    -o h3_fuzzer.o \
-    -c $SRC/h3_fuzzer.c
+make -j$(nproc) h3
 
-$CC $CFLAGS $LIB_FUZZING_ENGINE -rdynamic \
-    h3_fuzzer.o \
-    -o $OUT/h3_fuzzer \
+H3_BASE=/src/h3/
+
+for fuzzer in $(find $H3_BASE/src/apps/fuzzers -name '*.c'); do
+  fuzzer_basename=$(basename -s .c $fuzzer)
+  # H3_USE_LIBFUZZER is needed so that H3 does not try to build its own
+  # implementation of `main`
+  $CC $CFLAGS -DH3_PREFIX="" \
+    -DH3_USE_LIBFUZZER=1 \
+    -I$H3_BASE/src/apps/applib/include \
+    -I$H3_BASE/src/h3lib/include \
+    -I$H3_BASE/build/src/h3lib/include \
+    -o $fuzzer_basename.o \
+    -c $fuzzer
+
+  $CC $CFLAGS $LIB_FUZZING_ENGINE -rdynamic \
+    $fuzzer_basename.o \
+    -o $OUT/$fuzzer_basename \
     lib/libh3.a
-
+done

projects/h3/h3_fuzzer.c

@@ -1,74 +0,0 @@
-/*
-# Copyright 2021 Google LLC
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#      http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-################################################################################
-*/
-
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-
-// for h3NeighborRotations
-#include "algos.h"
-#include "h3api.h"
-#include "utility.h"
-
-static const Direction DIGITS[7] = {CENTER_DIGIT,  K_AXES_DIGIT, J_AXES_DIGIT,
-                                    JK_AXES_DIGIT, I_AXES_DIGIT, IK_AXES_DIGIT,
-                                    IJ_AXES_DIGIT};
-
-int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
-  if (size < sizeof(H3Index)) {
-    return 0;
-  }
-  H3Index h3;
-  memcpy(&h3, data, sizeof(H3Index));
-
-  H3Index input[] = {h3, h3};
-  int inputSize = sizeof(input) / sizeof(H3Index);
-
-  // fuzz compactCells
-  H3Index *compacted = calloc(inputSize, sizeof(H3Index));
-  H3Error errCompact = compactCells(input, compacted, inputSize);
-
-  // fuzz uncompactCells
-  int compactedCount = 0;
-  for (int i = 0; i < inputSize; i++) {
-    if (compacted[i] != 0) {
-      compactedCount++;
-    }
-  }
-  if (compactedCount < 2) {
-    int uncompactRes = 10;
-    int64_t uncompactedSize;
-    H3Error err2 =
-        uncompactCellsSize(compacted, inputSize, uncompactRes, &uncompactedSize);
-
-    H3Index *uncompacted = calloc(uncompactedSize, sizeof(H3Index));
-    H3Error err3 = uncompactCells(compacted, compactedCount, uncompacted,
-                                  uncompactedSize, uncompactRes);
-    free(uncompacted);
-  }
-
-  // fuzz h3NeighborRotations
-  int rotations = 0;
-  for (int i = 0; i < 7; i++) {
-    H3Index neighborRotationsOut;
-    h3NeighborRotations(h3, DIGITS[i], &rotations, &neighborRotationsOut);
-  }
-  free(compacted);
-  return 0;
-}