libctf, ld, binutils: add textual error/warning reporting for libctf

This commit adds a long-missing piece of infrastructure to libctf: the
ability to report errors and warnings using all the power of printf,
rather than being restricted to one errno value.  Internally, libctf
calls ctf_err_warn() to add errors and warnings to a list: a new
iterator ctf_errwarning_next() then consumes this list one by one and
hands it to the caller, which can free it.  New errors and warnings are
added until the list is consumed by the caller or the ctf_file_t is
closed, so you can dump them at intervals.  The caller can of course
choose to print only those warnings it wants.  (I am not sure whether we
want objdump, readelf or ld to print warnings or not: right now I'm
printing them, but maybe we only want to print errors?  This entirely
depends on whether warnings are voluminous things describing e.g. the
inability to emit single types because of name clashes or something.
There are no users of this infrastructure yet, so it's hard to say.)

There is no internationalization here yet, but this at least adds a
place where internationalization can be added, to one of
ctf_errwarning_next or ctf_err_warn.

We also provide a new ctf_assert() function which uses this
infrastructure to provide non-fatal assertion failures while emitting an
assert-like string to the caller: to save space and avoid needlessly
duplicating unchanging strings, the assertion test is inlined but the
print-things-out failure case is not.  All assertions in libctf will be
converted to use this machinery in future commits and propagate
assertion-failure errors up, so that the linker in particular cannot be
killed by libctf assertion failures when it could perfectly well just
print warnings and drop the CTF section.

include/
	* ctf-api.h (ECTF_INTERNAL): Adjust error text.
	(ctf_errwarning_next): New.
libctf/
	* ctf-impl.h (ctf_assert): New.
	(ctf_err_warning_t): Likewise.
	(ctf_file_t) <ctf_errs_warnings>: Likewise.
	(ctf_err_warn): New prototype.
	(ctf_assert_fail_internal): Likewise.
	* ctf-inlines.h (ctf_assert_internal): Likewise.
	* ctf-open.c (ctf_file_close): Free ctf_errs_warnings.
	* ctf-create.c (ctf_serialize): Copy it on serialization.
	* ctf-subr.c (ctf_err_warn): New, add an error/warning.
	(ctf_errwarning_next): New iterator, free and pass back
	errors/warnings in succession.
	* libctf.ver (ctf_errwarning_next): Add.
ld/
	* ldlang.c (lang_ctf_errs_warnings): New, print CTF errors
	and warnings.  Assert when libctf asserts.
	(lang_merge_ctf): Call it.
	(land_write_ctf): Likewise.
binutils/
	* objdump.c (ctf_archive_member): Print CTF errors and warnings.
	* readelf.c (dump_ctf_archive_member): Likewise.

7 files changed, 147 insertions, 0 deletions

diff --git a/libctf/ChangeLog b/libctf/ChangeLog
index f3ac4cc..114d4e6 100644
--- a/libctf/ChangeLog
+++ b/libctf/ChangeLog
@@ -1,3 +1,18 @@
+2020-07-22  Nick Alcock  <nick.alcock@oracle.com>
+
+	* ctf-impl.h (ctf_assert): New.
+	(ctf_err_warning_t): Likewise.
+	(ctf_file_t) <ctf_errs_warnings>: Likewise.
+	(ctf_err_warn): New prototype.
+	(ctf_assert_fail_internal): Likewise.
+	* ctf-inlines.h (ctf_assert_internal): Likewise.
+	* ctf-open.c (ctf_file_close): Free ctf_errs_warnings.
+	* ctf-create.c (ctf_serialize): Copy it on serialization.
+	* ctf-subr.c (ctf_err_warn): New, add an error/warning.
+	(ctf_errwarning_next): New iterator, free and pass back
+	errors/warnings in succession.
+	* libctf.ver (ctf_errwarning_next): Add.
+
 2020-07-22  Egeyar Bagcioglu  <egeyar.bagcioglu@oracle.com>
 
 	* ctf-types.c (ctf_variable_iter): Fix error return.
diff --git a/libctf/ctf-create.c b/libctf/ctf-create.c
index d50367d..a538b2d 100644
--- a/libctf/ctf-create.c
+++ b/libctf/ctf-create.c
@@ -534,6 +534,7 @@ ctf_serialize (ctf_file_t *fp)
   nfp->ctf_ptrtab_len = fp->ctf_ptrtab_len;
   nfp->ctf_link_inputs = fp->ctf_link_inputs;
   nfp->ctf_link_outputs = fp->ctf_link_outputs;
+  nfp->ctf_errs_warnings = fp->ctf_errs_warnings;
   nfp->ctf_str_prov_offset = fp->ctf_str_prov_offset;
   nfp->ctf_syn_ext_strtab = fp->ctf_syn_ext_strtab;
   nfp->ctf_link_cu_mapping = fp->ctf_link_cu_mapping;
@@ -556,6 +557,7 @@ ctf_serialize (ctf_file_t *fp)
   fp->ctf_str_atoms = NULL;
   fp->ctf_prov_strtab = NULL;
   memset (&fp->ctf_dtdefs, 0, sizeof (ctf_list_t));
+  memset (&fp->ctf_errs_warnings, 0, sizeof (ctf_list_t));
   fp->ctf_add_processing = NULL;
   fp->ctf_ptrtab = NULL;
   fp->ctf_link_inputs = NULL;
diff --git a/libctf/ctf-impl.h b/libctf/ctf-impl.h
index eea5204..47a3927 100644
--- a/libctf/ctf-impl.h
+++ b/libctf/ctf-impl.h
@@ -70,6 +70,10 @@ extern "C"
 
 #endif
 
+#define ctf_assert(fp, expr)						\
+  _libctf_unlikely_ (ctf_assert_internal (fp, __FILE__, __LINE__,	\
+					  #expr, !!(expr)))
+
 /* libctf in-memory state.  */
 
 typedef struct ctf_fixed_hash ctf_hash_t; /* Private to ctf-hash.c.  */
@@ -195,6 +199,13 @@ typedef struct ctf_bundle
   ctf_dtdef_t *ctb_dtd;		/* CTF dynamic type definition (if any).  */
 } ctf_bundle_t;
 
+typedef struct ctf_err_warning
+{
+  ctf_list_t cew_list;		/* List forward/back pointers.  */
+  int cew_is_warning;		/* 1 if warning, 0 if error.  */
+  char *cew_text;		/* Error/warning text.  */
+} ctf_err_warning_t;
+
 /* Atoms associate strings with a list of the CTF items that reference that
    string, so that ctf_update() can instantiate all the strings using the
    ctf_str_atoms and then reassociate them with the real string later.
@@ -297,6 +308,7 @@ struct ctf_file
   unsigned long ctf_snapshots;	  /* ctf_snapshot() plus ctf_update() count.  */
   unsigned long ctf_snapshot_lu;  /* ctf_snapshot() call count at last update.  */
   ctf_archive_t *ctf_archive;	  /* Archive this ctf_file_t came from.  */
+  ctf_list_t ctf_errs_warnings;	  /* CTF errors and warnings.  */
   ctf_dynhash_t *ctf_link_inputs; /* Inputs to this link.  */
   ctf_dynhash_t *ctf_link_outputs; /* Additional outputs from this link.  */
   ctf_dynhash_t *ctf_link_type_mapping; /* Map input types to output types.  */
@@ -543,6 +555,11 @@ _libctf_printflike_ (1, 2)
 extern void ctf_dprintf (const char *, ...);
 extern void libctf_init_debug (void);
 
+_libctf_printflike_ (3, 4)
+extern void ctf_err_warn (ctf_file_t *, int is_warning, const char *, ...);
+extern void ctf_assert_fail_internal (ctf_file_t *, const char *,
+				      size_t, const char *);
+
 extern Elf64_Sym *ctf_sym_to_elf64 (const Elf32_Sym *src, Elf64_Sym *dst);
 extern const char *ctf_lookup_symbol_name (ctf_file_t *fp, unsigned long symidx);
 
diff --git a/libctf/ctf-inlines.h b/libctf/ctf-inlines.h
index a35b6cd..affc9f9 100644
--- a/libctf/ctf-inlines.h
+++ b/libctf/ctf-inlines.h
@@ -80,6 +80,16 @@ ctf_dynset_cinsert (ctf_dynset_t *h, const void *k)
   return ctf_dynset_insert (h, (void *) k);
 }
 
+static inline int
+ctf_assert_internal (ctf_file_t *fp, const char *file, size_t line,
+		     const char *exprstr, int expr)
+{
+  if (_libctf_unlikely_ (!expr))
+    ctf_assert_fail_internal (fp, file, line, exprstr);
+
+  return expr;
+}
+
 #ifdef	__cplusplus
 }
 #endif
diff --git a/libctf/ctf-open.c b/libctf/ctf-open.c
index f8eeaab..24899f0 100644
--- a/libctf/ctf-open.c
+++ b/libctf/ctf-open.c
@@ -1644,6 +1644,7 @@ ctf_file_close (ctf_file_t *fp)
 {
   ctf_dtdef_t *dtd, *ntd;
   ctf_dvdef_t *dvd, *nvd;
+  ctf_err_warning_t *err, *nerr;
 
   if (fp == NULL)
     return;		   /* Allow ctf_file_close(NULL) to simplify caller code.  */
@@ -1710,6 +1711,14 @@ ctf_file_close (ctf_file_t *fp)
   ctf_dynhash_destroy (fp->ctf_link_cu_mapping);
   ctf_dynhash_destroy (fp->ctf_add_processing);
 
+  for (err = ctf_list_next (&fp->ctf_errs_warnings); err != NULL; err = nerr)
+    {
+      nerr = ctf_list_next (err);
+      ctf_list_delete (&fp->ctf_errs_warnings, err);
+      free (err->cew_text);
+      free (err);
+    }
+
   free (fp->ctf_sxlate);
   free (fp->ctf_txlate);
   free (fp->ctf_ptrtab);
diff --git a/libctf/ctf-subr.c b/libctf/ctf-subr.c
index a5cde9d..0b49ae9 100644
--- a/libctf/ctf-subr.c
+++ b/libctf/ctf-subr.c
@@ -194,3 +194,96 @@ void ctf_dprintf (const char *format, ...)
       va_end (alist);
     }
 }
+
+/* Errors and warnings.  */
+_libctf_printflike_ (3, 4)
+extern void
+ctf_err_warn (ctf_file_t *fp, int is_warning, const char *format, ...)
+{
+  va_list alist;
+  ctf_err_warning_t *cew;
+
+  /* Don't bother reporting errors here: we can't do much about them if they
+     happen.  If we're so short of memory that a tiny malloc doesn't work, a
+     vfprintf isn't going to work either and the caller will have to rely on the
+     ENOMEM return they'll be getting in short order anyway.  */
+
+  if ((cew = malloc (sizeof (ctf_err_warning_t))) == NULL)
+    return;
+
+  cew->cew_is_warning = is_warning;
+  va_start (alist, format);
+  if (vasprintf (&cew->cew_text, format, alist) < 0)
+    {
+      free (cew);
+      va_end (alist);
+      return;
+    }
+  va_end (alist);
+
+  ctf_dprintf ("%s: %s\n", is_warning ? "error" : "warning", cew->cew_text);
+
+  ctf_list_append (&fp->ctf_errs_warnings, cew);
+}
+
+/* Error-warning reporting: an 'iterator' that returns errors and warnings from
+   the error/warning list, in order of emission.  Errors and warnings are popped
+   after return: the caller must free the returned error-text pointer.  */
+char *
+ctf_errwarning_next (ctf_file_t *fp, ctf_next_t **it, int *is_warning)
+{
+  ctf_next_t *i = *it;
+  char *ret;
+  ctf_err_warning_t *cew;
+
+  if (!i)
+    {
+      if ((i = ctf_next_create ()) == NULL)
+	{
+	  ctf_set_errno (fp, ENOMEM);
+	  return NULL;
+	}
+
+      i->cu.ctn_fp = fp;
+      i->ctn_iter_fun = (void (*) (void)) ctf_errwarning_next;
+      *it = i;
+    }
+
+  if ((void (*) (void)) ctf_errwarning_next != i->ctn_iter_fun)
+    {
+      ctf_set_errno (fp, ECTF_NEXT_WRONGFUN);
+      return NULL;
+    }
+
+  if (fp != i->cu.ctn_fp)
+    {
+      ctf_set_errno (fp, ECTF_NEXT_WRONGFP);
+      return NULL;
+    }
+
+  cew = ctf_list_next (&fp->ctf_errs_warnings);
+
+  if (!cew)
+    {
+      ctf_next_destroy (i);
+      *it = NULL;
+      ctf_set_errno (fp, ECTF_NEXT_END);
+      return NULL;
+    }
+
+  if (is_warning)
+    *is_warning = cew->cew_is_warning;
+  ret = cew->cew_text;
+  ctf_list_delete (&fp->ctf_errs_warnings, cew);
+  free (cew);
+  return ret;
+}
+
+void
+ctf_assert_fail_internal (ctf_file_t *fp, const char *file, size_t line,
+			  const char *exprstr)
+{
+  ctf_err_warn (fp, 0, "%s: %lu: libctf assertion failed: %s", file,
+		(long unsigned int) line, exprstr);
+  ctf_set_errno (fp, ECTF_INTERNAL);
+}
diff --git a/libctf/libctf.ver b/libctf/libctf.ver
index e99f890..f1c9b2b 100644
--- a/libctf/libctf.ver
+++ b/libctf/libctf.ver
@@ -154,6 +154,7 @@ LIBCTF_1.0 {
 
 	ctf_setdebug;
 	ctf_getdebug;
+	ctf_errwarning_next;
 
 	/* Not yet part of the stable API.  */