From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Tue, 2 Jul 2019 15:09:39 +0000 (-0600)
Subject: Add a couple of comments to functions in utilities.cc.
X-Git-Tag: v9.2.0-rc1~1415^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F8336%2Fhead;p=dealii.git

Add a couple of comments to functions in utilities.cc.
---

diff --git a/source/base/utilities.cc b/source/base/utilities.cc
index 08f40984cb..fbf823f7be 100644
--- a/source/base/utilities.cc
+++ b/source/base/utilities.cc
@@ -494,15 +494,24 @@ namespace Utilities
     while ((s.size() > 0) && (s[s.size() - 1] == ' '))
       s.erase(s.end() - 1);
 
-    // now convert and see whether we succeed. note that strtol only
+    // Now convert and see whether we succeed. Note that strtol only
     // touches errno if an error occurred, so if we want to check
     // whether an error happened, we need to make sure that errno==0
     // before calling strtol since otherwise it may be that the
     // conversion succeeds and that errno remains at the value it
-    // was before, whatever that was
+    // was before, whatever that was.
     char *p;
     errno       = 0;
     const int i = std::strtol(s.c_str(), &p, 10);
+
+    // We have an error if one of the following conditions is true:
+    // - strtol sets errno != 0
+    // - The original string was empty (we could have checked that
+    //   earlier already)
+    // - The string has non-zero length and strtol converted the
+    //   first part to something useful, but stopped converting short
+    //   of the terminating '\0' character. This happens, for example,
+    //   if the given string is "1234 abc".
     AssertThrow(!((errno != 0) || (s.size() == 0) ||
                   ((s.size() > 0) && (*p != '\0'))),
                 ExcMessage("Can't convert <" + s + "> to an integer."));
@@ -533,15 +542,24 @@ namespace Utilities
     while ((s.size() > 0) && (s[s.size() - 1] == ' '))
       s.erase(s.end() - 1);
 
-    // now convert and see whether we succeed. note that strtol only
+    // Now convert and see whether we succeed. Note that strtol only
     // touches errno if an error occurred, so if we want to check
     // whether an error happened, we need to make sure that errno==0
     // before calling strtol since otherwise it may be that the
     // conversion succeeds and that errno remains at the value it
-    // was before, whatever that was
+    // was before, whatever that was.
     char *p;
     errno          = 0;
     const double d = std::strtod(s.c_str(), &p);
+
+    // We have an error if one of the following conditions is true:
+    // - strtod sets errno != 0
+    // - The original string was empty (we could have checked that
+    //   earlier already)
+    // - The string has non-zero length and strtod converted the
+    //   first part to something useful, but stopped converting short
+    //   of the terminating '\0' character. This happens, for example,
+    //   if the given string is "1.234 abc".
     AssertThrow(!((errno != 0) || (s.size() == 0) ||
                   ((s.size() > 0) && (*p != '\0'))),
                 ExcMessage("Can't convert <" + s + "> to a double."));