Commit 2e34efaab1ec85a5a4ba522147edec9114d065d3
2018-10-21T13:10:06
buf::oom tests: use custom allocator for oom failures Create a custom allocator for the `buf::oom` tests that will fail with out-of-memory errors in predictable ways. We were previously trying to guess the way that various allocators on various platforms would fail in a way such that `malloc`/`realloc` would return `NULL` (instead of aborting the application, or appearing suspicious to various instrumentation or static code analysis tools like valgrind.) Introduce a fake `malloc` and `realloc` that will return `NULL` on allocations requesting more than 100 bytes. Otherwise, we proxy to the default allocator. (It's important to use the _default_ allocator, not just call `malloc`, since the default allocator on Windows CI builds may be the debugging C runtime allocators which would not be compatible with a standard `malloc`.)
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diff --git a/tests/buf/oom.c b/tests/buf/oom.c
index ec3bad9..726234e 100644
--- a/tests/buf/oom.c
+++ b/tests/buf/oom.c
@@ -1,57 +1,59 @@
#include "clar_libgit2.h"
#include "buffer.h"
-/*
- * We want to use some ridiculous size that `malloc` will fail with
- * but that does not otherwise interfere with testing. On Linux, choose
- * a number that is large enough to fail immediately but small enough
- * that valgrind doesn't believe it to erroneously be a negative number.
- * On macOS, choose a number that is large enough to fail immediately
- * without having libc print warnings to stderr.
- */
-#if defined(GIT_ARCH_64) && defined(__linux__)
-# define TOOBIG 0x0fffffffffffffff
-#elif defined(GIT_ARCH_64)
-# define TOOBIG 0xffffffffffffff00
-#endif
-
-/**
- * If we make a ridiculously large request the first time we
- * actually allocate some space in the git_buf, the realloc()
- * will fail. And because the git_buf_grow() wrapper always
- * sets mark_oom, the code in git_buf_try_grow() will free
- * the internal buffer and set it to git_buf__oom.
- *
- * We initialized the internal buffer to (the static variable)
- * git_buf__initbuf. The purpose of this test is to make sure
- * that we don't try to free the static buffer.
- *
- * Skip this test entirely on 32-bit platforms; a buffer large enough
- * to guarantee malloc failures is so large that valgrind considers
- * it likely to be an error.
- */
+/* Override default allocators with ones that will fail predictably. */
+
+static git_allocator std_alloc;
+static git_allocator oom_alloc;
+
+static void *oom_malloc(size_t n, const char *file, int line)
+{
+ /* Reject any allocation of more than 100 bytes */
+ return (n > 100) ? NULL : std_alloc.gmalloc(n, file, line);
+}
+
+static void *oom_realloc(void *p, size_t n, const char *file, int line)
+{
+ /* Reject any allocation of more than 100 bytes */
+ return (n > 100) ? NULL : std_alloc.grealloc(p, n, file, line);
+}
+
+void test_buf_oom__initialize(void)
+{
+ git_stdalloc_init_allocator(&std_alloc);
+ git_stdalloc_init_allocator(&oom_alloc);
+
+ oom_alloc.gmalloc = oom_malloc;
+ oom_alloc.grealloc = oom_realloc;
+
+ cl_git_pass(git_libgit2_opts(GIT_OPT_SET_ALLOCATOR, &oom_alloc));
+}
+
+void test_buf_oom__cleanup(void)
+{
+ cl_git_pass(git_libgit2_opts(GIT_OPT_SET_ALLOCATOR, NULL));
+}
+
void test_buf_oom__grow(void)
{
-#ifdef GIT_ARCH_64
git_buf buf = GIT_BUF_INIT;
- git_buf_clear(&buf);
+ cl_git_pass(git_buf_grow(&buf, 42));
+ cl_assert(!git_buf_oom(&buf));
- cl_assert(git_buf_grow(&buf, TOOBIG) == -1);
+ cl_assert(git_buf_grow(&buf, 101) == -1);
cl_assert(git_buf_oom(&buf));
git_buf_dispose(&buf);
-#else
- cl_skip();
-#endif
}
void test_buf_oom__grow_by(void)
{
git_buf buf = GIT_BUF_INIT;
- buf.size = SIZE_MAX-10;
+ cl_git_pass(git_buf_grow_by(&buf, 42));
+ cl_assert(!git_buf_oom(&buf));
- cl_assert(git_buf_grow_by(&buf, 50) == -1);
+ cl_assert(git_buf_grow_by(&buf, 101) == -1);
cl_assert(git_buf_oom(&buf));
}