[groff] 73/115: [troff]: Skip allocation of zero-length arrays.

[G. Branden Robinson]

gbranden pushed a commit to branch branden-2022-06-01
in repository groff.

commit 8b7692a54e0cf5ffec26c52ea621ebf4a4620d32
Author: G. Branden Robinson <g.branden.robinson@gmail.com>
AuthorDate: Mon Apr 3 19:30:56 2023 -0500

    [troff]: Skip allocation of zero-length arrays.
    
    * src/roff/troff/input.cpp (temp_iterator::temp_iterator): Skip
      allocation of zero-length arrays.  Resolves "-Walloc-zero" warning
      from GCC.
    
    Fixes <https://savannah.gnu.org/bugs/?62398>.  Thanks to Bjarni Ingi
    Gislason for the report.
    
    It is not necessary to make conditional the subsequent `delete[]` of a
    null pointer.  "If the _delete-expression_ calls the implementation
    deallocation function (3.7.3.2), and if the operand of the delete
    expression is not the null pointer constant, the deallocation function
    will deallocate the storage referenced by the pointer thus rendering the
    pointer invalid" (ISO/IEC 14882-1998, §5.3.5, paragraph 4).  Or as
    Stroustrup puts it, "Applying _delete_ to zero has no effect." (_The C++
    Programming Language, Special Edition_, p. 128).
    
    Also annotate some null pointers with `nullptr` comments to ease any
    future transition to C++11, which defines it as a keyword.
---
 ChangeLog                |  9 +++++++++
 src/roff/troff/input.cpp | 14 ++++++++------
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index b0fabd6b4..2f92a7f2f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2023-04-03  G. Branden Robinson <g.branden.robinson@gmail.com>
+
+       * src/roff/troff/input.cpp (temp_iterator::temp_iterator):
+       Skip allocation of zero-length arrays.  Resolves "-Walloc-zero"
+       warning from GCC.
+
+       Fixes <https://savannah.gnu.org/bugs/?62398>.  Thanks to Bjarni
+       Ingi Gislason for the report.
+
 2023-04-02  G. Branden Robinson <g.branden.robinson@gmail.com>
 
        * src/roff/troff/input.cpp (token::description): Revise
diff --git a/src/roff/troff/input.cpp b/src/roff/troff/input.cpp
index 2a86c9c01..5f110e0bc 100644
--- a/src/roff/troff/input.cpp
+++ b/src/roff/troff/input.cpp
@@ -234,12 +234,12 @@ private:
 };
 
 input_iterator::input_iterator()
-: is_diversion(0), ptr(0), eptr(0)
+: is_diversion(0), ptr(0 /* nullptr */), eptr(0 /* nullptr */)
 {
 }
 
 input_iterator::input_iterator(int is_div)
-: is_diversion(is_div), ptr(0), eptr(0)
+: is_diversion(is_div), ptr(0 /* nullptr */), eptr(0 /* nullptr */)
 {
 }
 
@@ -3627,12 +3627,14 @@ public:
 inline
 #endif
 temp_iterator::temp_iterator(const char *s, int len)
+: base(0 /* nullptr */)
 {
-  base = new unsigned char[len];
-  if (len > 0)
+  if (len > 0) {
+    base = new unsigned char[len];
     memcpy(base, s, len);
-  ptr = base;
-  eptr = base + len;
+    ptr = base;
+    eptr = base + len;
+  }
 }
 
 temp_iterator::~temp_iterator()