Support musl libc in the test drivers' standard library tables

c2mir-driver.c, mir-bin-run.c, and mir-bin-driver.c resolve external
symbols for executed programs by dlopening hardcoded glibc paths
(/lib64/libc.so.6, /lib/<triplet>-linux-gnu/libc.so.6, ...), so on musl
distributions like Alpine every executed test fails with e.g. "can not
load symbol printf" (issue #307), and mir-bin-driver exits before
running anything.  On musl, libc, libm, libpthread, and libdl are all
one shared object installed as the dynamic loader
/lib/ld-musl-<arch>.so.1: add that path (selected by
__linux__ && !__GLIBC__) to all three tables.

Fixes #307.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: cyanogilvie

c2mir/c2mir-driver.c

@@ -65,7 +65,29 @@ struct lib {
 typedef struct lib lib_t;
 
 #if defined(__unix__)
-#if UINTPTR_MAX == 0xffffffff
+#if defined(__linux__) && !defined(__GLIBC__)
+/* A non-glibc Linux libc, e.g. musl on Alpine: libc, libm, libpthread, and
+   libdl all live in one shared object, installed as the dynamic loader
+   /lib/ld-musl-<arch>.so.1 on musl.  */
+#if defined(__x86_64__)
+#define MUSL_LIB_ARCH "x86_64"
+#elif defined(__aarch64__)
+#define MUSL_LIB_ARCH "aarch64"
+#elif defined(__PPC64__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define MUSL_LIB_ARCH "powerpc64le"
+#elif defined(__PPC64__)
+#define MUSL_LIB_ARCH "powerpc64"
+#elif defined(__s390x__)
+#define MUSL_LIB_ARCH "s390x"
+#elif defined(__riscv)
+#define MUSL_LIB_ARCH "riscv64"
+#else
+#error cannot recognize the non-glibc linux target
+#endif
+static lib_t std_libs[]
+  = {{"/lib/ld-musl-" MUSL_LIB_ARCH ".so.1", NULL}, {"/usr/lib/libc.so", NULL}};
+static const char *std_lib_dirs[] = {"/lib", "/usr/lib"};
+#elif UINTPTR_MAX == 0xffffffff
 static lib_t std_libs[]
   = {{"/lib/libc.so", NULL},         {"/lib/libm.so", NULL},          {"/lib/libc.so.6", NULL},
      {"/lib32/libc.so.6", NULL},     {"/lib/libm.so.6", NULL},        {"/lib32/libm.so.6", NULL},

mir-bin-driver.c

@@ -24,7 +24,25 @@ static struct lib {
   char *name;
   void *handler;
 } libs[] = {
-#if !defined(__APPLE__)
+#if defined(__linux__) && !defined(__GLIBC__)
+/* A non-glibc Linux libc, e.g. musl on Alpine: everything lives in one
+   shared object, installed as the dynamic loader on musl.  */
+#if defined(__x86_64__)
+  {"/lib/ld-musl-x86_64.so.1", NULL}
+#elif defined(__aarch64__)
+  {"/lib/ld-musl-aarch64.so.1", NULL}
+#elif defined(__PPC64__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  {"/lib/ld-musl-powerpc64le.so.1", NULL}
+#elif defined(__PPC64__)
+  {"/lib/ld-musl-powerpc64.so.1", NULL}
+#elif defined(__s390x__)
+  {"/lib/ld-musl-s390x.so.1", NULL}
+#elif defined(__riscv)
+  {"/lib/ld-musl-riscv64.so.1", NULL}
+#else
+#error cannot recognize the non-glibc linux target
+#endif
+#elif !defined(__APPLE__)
   {"/lib64/libc.so.6", NULL}, {"/lib64/libm.so.6", NULL}, {"/lib64/libpthread.so.0", NULL}
 #else
   {"/usr/lib/libc.dylib", NULL}, {"/usr/lib/libm.dylib", NULL}

mir-bin-run.c

@@ -28,7 +28,29 @@ typedef struct lib lib_t;
 
 /* stdlibs according to c2mir */
 #if defined(__unix__)
-#if UINTPTR_MAX == 0xffffffff
+#if defined(__linux__) && !defined(__GLIBC__)
+/* A non-glibc Linux libc, e.g. musl on Alpine: libc, libm, libpthread, and
+   libdl all live in one shared object, installed as the dynamic loader
+   /lib/ld-musl-<arch>.so.1 on musl.  */
+#if defined(__x86_64__)
+#define MUSL_LIB_ARCH "x86_64"
+#elif defined(__aarch64__)
+#define MUSL_LIB_ARCH "aarch64"
+#elif defined(__PPC64__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define MUSL_LIB_ARCH "powerpc64le"
+#elif defined(__PPC64__)
+#define MUSL_LIB_ARCH "powerpc64"
+#elif defined(__s390x__)
+#define MUSL_LIB_ARCH "s390x"
+#elif defined(__riscv)
+#define MUSL_LIB_ARCH "riscv64"
+#else
+#error cannot recognize the non-glibc linux target
+#endif
+static lib_t std_libs[]
+  = {{"/lib/ld-musl-" MUSL_LIB_ARCH ".so.1", NULL}, {"/usr/lib/libc.so", NULL}};
+static const char *std_lib_dirs[] = {"/lib", "/usr/lib"};
+#elif UINTPTR_MAX == 0xffffffff
 static lib_t std_libs[]
   = {{"/lib/libc.so.6", NULL},   {"/lib32/libc.so.6", NULL},     {"/lib/libm.so.6", NULL},
      {"/lib32/libm.so.6", NULL}, {"/lib/libpthread.so.0", NULL}, {"/lib32/libpthread.so.0", NULL}};