Merge branch 'patch-1' into 'master'

Clean up everything and add lots of new functions

I hope everything here is okay. I fixed some bugs in existing functions (mostly wrong prototypes or off-by-one errors) and formatted everything to a consistent style. If you'd like me to adjust the style, that's no problem. It wasn't very consistent to start with (within the code, and compared to the documentation).

*I added specific notes you may want to comment on to some of the commit messages.*

Major features:
* Pass correct `argv[0]` in loader
* Intercept `readlink("/proc/self/exe")` to allow re-exec
* Add almost all reasonable-to-implement functions in LSB 5.0.0 core generic libc. Remaining functions are:
  - Impossible-to-implement: sigreturn
  - Not useful: reentrant random (`*rand48_r`, etc.), argz, envz, pmap, rpc (clnt_*, svc*, xdr*), bindresvport
  - Got tired of it: checked wchar
* Add additional functions used by android and its NDK tools (clang, cmake, lldb, ninja, etc.).

At this point, I am able to run Android Studio with the bundled prebuilt JDK, and compile, install, and run an android application (including one with native libraries) on a real device, with only a few minor issues:
* must export `LD_LIBRARY_PATH=/opt/android-studio/jre/jre/lib/amd64/server` because musl and glibc interpret the variable differently with regards to `dlopen`. This is something that has to be patched in musl builds of openjdk, so it's not a gcompat issue.
* ld.bfd fails to parse the argument `--sysroot=/path`, but can parse `--sysroot /path`. So there's some difference with `getopt_long_only` (or getopt in general). May be a bug, may be just an API difference. May be it can be patched up.
* LLDB fails to connect to the android phone for native debugging -- I haven't tried it on glibc yet, so it may not be a gcompat issue at all (may be a phone or the app issue).

I'd be happy to send some documentation later.

See merge request !1

1 files changed, 97 insertions, 0 deletions

diff --git a/libgcompat/execinfo.c b/libgcompat/execinfo.c
new file mode 100644
index 0000000..59441aa
--- /dev/null
+++ b/libgcompat/execinfo.c
@@ -0,0 +1,97 @@
+#include <dlfcn.h>  /* dladdr */
+#include <stddef.h> /* NULL */
+#include <stdint.h> /* uintptr_t */
+#include <stdlib.h> /* calloc */
+#include <string.h> /* strlen */
+#include <unistd.h> /* write */
+
+#define get_frame_level(array, size, n)                                        \
+	do {                                                                   \
+		if (n >= size || __builtin_frame_address(n) == NULL) {         \
+			return n;                                              \
+		}                                                              \
+		void *address = __builtin_return_address(n);                   \
+		array[n] = __builtin_extract_return_addr(address);             \
+		if ((uintptr_t) array[n] < 0x1000) {                           \
+			return n;                                              \
+		}                                                              \
+	} while (0)
+
+/**
+ * Obtain a backtrace for the calling program.
+ *
+ * LSB 5.0: LSB-Core-generic/baselib-backtrace-1.html
+ */
+int backtrace(void **array, int size)
+{
+	get_frame_level(array, size, 0);
+	get_frame_level(array, size, 1);
+	get_frame_level(array, size, 2);
+	get_frame_level(array, size, 3);
+	get_frame_level(array, size, 4);
+	get_frame_level(array, size, 5);
+	get_frame_level(array, size, 6);
+	get_frame_level(array, size, 7);
+	get_frame_level(array, size, 8);
+	get_frame_level(array, size, 9);
+	return 10;
+}
+
+/**
+ * Translate addresses into symbol information.
+ *
+ * LSB 5.0: LSB-Core-generic/baselib-backtrace-1.html
+ */
+const char **backtrace_symbols(void *const *array, int size)
+{
+	const char **result = calloc(size, sizeof(char *));
+
+	if (result == NULL) {
+		return NULL;
+	}
+	for (int i = 0; i < size; ++i) {
+		Dl_info info;
+
+		if (dladdr(array[i], &info) && info.dli_sname != NULL) {
+			result[i] = info.dli_sname;
+		} else {
+			result[i] = "??:0";
+		}
+	}
+
+	return result;
+}
+
+/**
+ * Write symbol information to a file without allocating memory.
+ *
+ * LSB 5.0: LSB-Core-generic/baselib-backtrace-1.html
+ */
+void backtrace_symbols_fd(void *const *array, int size, int fd)
+{
+	for (int i = 0; i < size; ++i) {
+		Dl_info info;
+		const char *line;
+		int len;
+
+		if (dladdr(array[i], &info) && info.dli_sname != NULL) {
+			line = info.dli_sname;
+			len = strlen(line);
+		} else {
+			line = "??:0";
+			len = sizeof("??:0") - 1;
+		}
+		while (len > 0) {
+			int written = write(fd, line, len);
+
+			if (written < 1) {
+				return;
+			}
+			line += written;
+			len -= written;
+		}
+		if (write(fd, "\n", 1) != 1) {
+			return;
+		}
+	}
+}