[gcc/devel/gccgo] libbacktrace: support short read

[Ian Lance Taylor]

https://gcc.gnu.org/g:4b26b13871a672059d1bdebbc4d87a4429c5abd8

commit 4b26b13871a672059d1bdebbc4d87a4429c5abd8
Author: Ian Lance Taylor <iant@golang.org>
Date:   Sat Feb 15 18:13:28 2020 -0800

    libbacktrace: support short read
    
            * read.c (backtrace_get_view): Support short read.

Diff:
---
 libbacktrace/ChangeLog |  4 ++++
 libbacktrace/read.c    | 22 +++++++++++++++-------
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/libbacktrace/ChangeLog b/libbacktrace/ChangeLog
index 277d7c01ff3..4b4f574fc75 100644
--- a/libbacktrace/ChangeLog
+++ b/libbacktrace/ChangeLog
@@ -1,3 +1,7 @@
+2020-05-09  Ian Lance Taylor  <iant@golang.org>
+
+	* read.c (backtrace_get_view): Support short read.
+
 2020-05-09  Ian Lance Taylor  <iant@golang.org>
 
 	* elf.c (elf_add): If debug sections are very large or far apart,
diff --git a/libbacktrace/read.c b/libbacktrace/read.c
index 57e4701bbeb..1a6052bf613 100644
--- a/libbacktrace/read.c
+++ b/libbacktrace/read.c
@@ -50,7 +50,8 @@ backtrace_get_view (struct backtrace_state *state, int descriptor,
 		    backtrace_error_callback error_callback,
 		    void *data, struct backtrace_view *view)
 {
-  ssize_t got;
+  uint64_t got;
+  ssize_t r;
 
   if ((uint64_t) (size_t) size != size)
     {
@@ -70,15 +71,22 @@ backtrace_get_view (struct backtrace_state *state, int descriptor,
   view->data = view->base;
   view->len = size;
 
-  got = read (descriptor, view->base, size);
-  if (got < 0)
+  got = 0;
+  while (got < size)
     {
-      error_callback (data, "read", errno);
-      free (view->base);
-      return 0;
+      r = read (descriptor, view->base, size - got);
+      if (r < 0)
+	{
+	  error_callback (data, "read", errno);
+	  free (view->base);
+	  return 0;
+	}
+      if (r == 0)
+	break;
+      got += (uint64_t) r;
     }
 
-  if ((size_t) got < size)
+  if (got < size)
     {
       error_callback (data, "file too short", 0);
       free (view->base);