build: avoid false -Wmaybe-uninitialized warnings

Allow easily building a debug build for example with:
  make CFLAGS='-O0 -ggdb'

False -Wmaybe-uninitialized warnings hit in different
places depending on the compiler passes used.
These changes were tested with gcc 10.2.1, 12.2.1, and 13.1.1 like:
  for o in g s z fast 0 1 2 3; do
    make clean && make -j$(nproc) CFLAGS="-O$o" || break
  done

* src/digest.c: Disable -Wmaybe-uninitialized that gives
false positive here at -O0.
* src/ln.c: Avoid -Wmaybe-uninitialized that gives
false positive here at -O1.
* src/pr.c: Likewise.
* src/sort.c: Likewise.
* src/tee.c: Avoid -Wmaybe-uninitialized that gives
false positive here at -O3 on gcc 13.1.1 at least.
* src/cp.c: Avoid -Wmaybe-uninitialized that gives
false positive here at -Os on gcc 13.1.1 at least.
* src/copy.c: Avoid -Wmaybe-uninitialized that gives
false positive here at -Og on gcc 13.1.1 at least.
* src/head.c: Likewise.
* src/paste.c: Likewise.

9 files changed, 12 insertions, 9 deletions

diff --git a/src/copy.c b/src/copy.c
index 0dd059d2e..6b2cf3b29 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -1238,8 +1238,8 @@ copy_reg (char const *src_name, char const *dst_name,
           struct stat const *src_sb)
 {
   char *buf = NULL;
-  int dest_desc;
-  int dest_errno;
+  int dest_desc IF_LINT ( = -1);
+  int dest_errno IF_LINT ( = 0);
   int source_desc;
   mode_t src_mode = src_sb->st_mode;
   mode_t extra_permissions;
diff --git a/src/cp.c b/src/cp.c
index 619eb8260..c952eb397 100644
--- a/src/cp.c
+++ b/src/cp.c
@@ -441,7 +441,7 @@ make_dir_parents_private (char const *const_dir, size_t src_offset,
 
       while ((slash = strchr (slash, '/')))
         {
-          struct dir_attr *new;
+          struct dir_attr *new IF_LINT ( = NULL);
           bool missing_dir;
 
           *slash = '\0';
diff --git a/src/digest.c b/src/digest.c
index ab32968db..6d9cc2a5b 100644
--- a/src/digest.c
+++ b/src/digest.c
@@ -1125,6 +1125,9 @@ hex_equal (unsigned char const *hex_digest, unsigned char const *bin_buffer)
   return cnt == digest_bin_bytes;
 }
 
+#if defined __GNUC__ && (__GNUC__ + (__GNUC_MINOR__ >= 7) > 4)
+# pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+#endif
 static bool
 digest_check (char const *checkfile_name)
 {
diff --git a/src/head.c b/src/head.c
index c9d3b0d05..f576a2200 100644
--- a/src/head.c
+++ b/src/head.c
@@ -351,7 +351,7 @@ elide_tail_bytes_pipe (char const *filename, int fd, uintmax_t n_elide_0,
          bytes.  Then, for each new buffer we read, also write an old one.  */
 
       bool eof = false;
-      size_t n_read;
+      size_t n_read IF_LINT ( = 0);
       bool buffered_enough;
       size_t i, i_next;
       char **b = NULL;
diff --git a/src/ln.c b/src/ln.c
index 1c3307cac..bfdac0cd9 100644
--- a/src/ln.c
+++ b/src/ln.c
@@ -473,7 +473,7 @@ main (int argc, char **argv)
   char const *backup_suffix = NULL;
   char *version_control_string = NULL;
   char const *target_directory = NULL;
-  int destdir_fd;
+  int destdir_fd IF_LINT ( = -1);
   bool no_target_directory = false;
   int n_files;
   char **file;
diff --git a/src/paste.c b/src/paste.c
index 5c194d8fe..468ef3ab0 100644
--- a/src/paste.c
+++ b/src/paste.c
@@ -233,7 +233,7 @@ paste_parallel (size_t nfiles, char **fnamptr)
 
       for (size_t i = 0; i < nfiles && files_open; i++)
         {
-          int chr;			/* Input character. */
+          int chr IF_LINT ( = -1);	/* Input character. */
           int err;			/* Input errno value.  */
           bool sometodo = false;	/* Input chars to process.  */
 
diff --git a/src/pr.c b/src/pr.c
index 1c32e8c81..6be5b1f33 100644
--- a/src/pr.c
+++ b/src/pr.c
@@ -2428,7 +2428,7 @@ static bool
 read_line (COLUMN *p)
 {
   int c;
-  int chars;
+  int chars IF_LINT ( =0);
   int last_input_position;
   int j, k;
   COLUMN *q;
diff --git a/src/sort.c b/src/sort.c
index 8ca7a88c4..5aadc797b 100644
--- a/src/sort.c
+++ b/src/sort.c
@@ -1045,7 +1045,7 @@ pipe_fork (int pipefds[2], size_t tries)
   struct tempnode *saved_temphead;
   int saved_errno;
   double wait_retry = 0.25;
-  pid_t pid;
+  pid_t pid IF_LINT ( = -1);
   struct cs_status cs;
 
   if (pipe2 (pipefds, O_CLOEXEC) < 0)
diff --git a/src/tee.c b/src/tee.c
index a1c057816..27e83619e 100644
--- a/src/tee.c
+++ b/src/tee.c
@@ -228,7 +228,7 @@ tee_files (int nfiles, char **files, bool pipe_check)
 {
   size_t n_outputs = 0;
   FILE **descriptors;
-  bool *out_pollable;
+  bool *out_pollable IF_LINT ( = NULL);
   char buffer[BUFSIZ];
   ssize_t bytes_read = 0;
   int i;