This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH] print full STRING_CST in Gimple dumps (PR 87052)


On 08/23/2018 08:07 AM, Michael Matz wrote:
Hi,

On Thu, 23 Aug 2018, Richard Biener wrote:

Can you write a not \0 terminated string literal in C?

Yes: char a[2] = "12";

I thought they are fully defined in translation phase #1 ...

No, you can't write a string literal which is not zero terminated, because
in translation phase 7 a zero code is appended to all character sequences
resulting from string literals, which is then used to allocate and
initialize a static (wide) character array of just the right size,
including the zero code.

The above construct uses that static char[3] array from the string literal
to initialize a char[2] array (which is explicitely allowed), and _that_
one is not zero terminated.  But it's also no string literal.

Yes, you're right.  I misinterpreted Richard's question as
asking if one could construct an unterminated array of chars
using a string literal.

The distinction that I thought would be useful to capture in
Gimple is between "12" that initializes an array of two elements
(and where the nul doesn't fit) vs "12" that initializes one of
three elements (and where the nul does fit).  It's probably not
terribly important when the array type also appears in Gimple
like in the case above but there are (perhaps corner) cases
where it doesn't, as in the second one below:

  char a[2] = "12";
  char *p = (char[2]){ "12" };

which ends up represented as:

  char a[2];
  char * p;
  char D.1910[2];

  try
    {
      a = "12";
      D.1910 = "12";
      p = &D.1910;
    }

Martin


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]