[committed] Change files var in main to char **

[Tom de Vries <tdevries@suse.de>]

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[ was: Re: [committed] Make main more readable ]

On 3/18/21 7:52 PM, Florian Weimer wrote:
> * Tom de Vries:
> 
>> I've prepared a patch implementing that suggestion.  Does that address
>> your concerns?
>>
>> [ FWIW, I've read through a C99 draft pdf to refresh my memory on this
>> topic.  Looking at the effective type of **argv, AFAIU it falls into the
>> catagory "For all other accesses to an object having no declared type,
>> the effective type of the object is simply the type of the lvalue used
>> for the access".  In other words, the effective type is char.
>>
>> Then I read:
>> ...
>> An object shall have its stored value accessed only by an lvalue
>> expression that has one of the following types:
>> — a qualified version of a type compatible with the effective type of
>>   the object,
>> ...
>>
>> So, const char is a qualified version of a type char compatible with the
>> effective type of the object (char).
>>
>> So I still don't see the problem. ]
> 
> I think the issue is about the char * array elements, not the individual
> bytes in the strings themselves.

I see, that explains, I somehow managed to miss that.

I've updated the log message, and committed.

Thanks,
- Tom


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Change files var in main to char **

The cast on &argv[optind] to const char **:
...
main (int argc, char *argv[])
{
  ...
  const char **files;
  ...
  files = (const char **)&argv[optind];
...
violates the aliasing rules.

The array element argv[i] aliases with the array element files[i],
but the types of the elements (char * vs. const char *) are not compatible types.

Since we access the elements using both types (const char * in dwz_files/dwz,
char * in getopt_long), there's a violation.

Fix this by changing the type of files to char **.

2021-03-18  Tom de Vries  <tdevries@suse.de>

	* dwz.c (dwz): Make files param a char **.
	(dwz_files): Make files param char *[].
	(main): Make files var a char **.

---
 dwz.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/dwz.c b/dwz.c
index 7b67960..a7aa23b 100644
--- a/dwz.c
+++ b/dwz.c
@@ -15267,7 +15267,7 @@ struct file_result
    over FILE.  */
 static int
 dwz (const char *file, const char *outfile, struct file_result *res,
-     struct file_result *resa, const char **files)
+     struct file_result *resa, char **files)
 {
   DSO *dso;
   int ret = 0, fd;
@@ -16285,7 +16285,7 @@ dwz_one_file (const char *file, const char *outfile)
 /* Dwarf-compress FILES.  If HARDLINK, detect if some files are hardlinks and
    if so, dwarf-compress just one, and relink the others.  */
 static int
-dwz_files (int nr_files, const char *files[], bool hardlink)
+dwz_files (int nr_files, char *files[], bool hardlink)
 {
   int ret = 0;
   int i;
@@ -16413,7 +16413,7 @@ main (int argc, char *argv[])
   const char *outfile;
   bool hardlink;
   int nr_files;
-  const char **files;
+  char **files;
 
   if (elf_version (EV_CURRENT) == EV_NONE)
     error (1, 0, "library out of date");
@@ -16422,7 +16422,7 @@ main (int argc, char *argv[])
   hardlink = false;
   parse_args (argc, argv, &hardlink, &outfile);
   nr_files = argc - optind;
-  files = (const char **)&argv[optind];
+  files = &argv[optind];
 
   if (nr_files <= 1)
     {