MDEV-21907: InnoDB: Enable -Wconversion on clang and GCC

The -Wconversion in GCC seems to be stricter than in clang.
GCC at least since version 4.4.7 issues truncation warnings for
assignments to bitfields, while clang 10 appears to only issue
warnings when the sizes in bytes rounded to the nearest integer
powers of 2 are different.

Before GCC 10.0.0, -Wconversion required more casts and would not
allow some operations, such as x<<=1 or x+=1 on a data type that
is narrower than int.

GCC 5 (but not GCC 4, GCC 6, or any later version) is complaining
about x|=y even when x and y are compatible types that are narrower
than int.  Hence, we must rewrite some x|=y as
x=static_cast<byte>(x|y) or similar, or we must disable -Wconversion.

In GCC 6 and later, the warning for assigning wider to bitfields
that are narrower than 8, 16, or 32 bits can be suppressed by
applying a bitwise & with the exact bitmask of the bitfield.
For older GCC, we must disable -Wconversion for GCC 4 or 5 in such
cases.

The bitwise negation operator appears to promote short integers
to a wider type, and hence we must add explicit truncation casts
around them. Microsoft Visual C does not allow a static_cast to
truncate a constant, such as static_cast<byte>(1) truncating int.
Hence, we will use the constructor-style cast byte(~1) for such cases.

This has been tested at least with GCC 4.8.5, 5.4.0, 7.4.0, 9.2.1, 10.0.0,
clang 9.0.1, 10.0.0, and MSVC 14.22.27905 (Microsoft Visual Studio 2019)
on 64-bit and 32-bit targets (IA-32, AMD64, POWER 8, POWER 9, ARMv8).

3 files changed, 30 insertions, 43 deletions

diff --git a/extra/mariabackup/backup_mysql.cc b/extra/mariabackup/backup_mysql.cc
index 847340e6dc7..6c13079a8fc 100644
--- a/extra/mariabackup/backup_mysql.cc
+++ b/extra/mariabackup/backup_mysql.cc
@@ -505,7 +505,8 @@ get_mysql_vars(MYSQL *connection)
 	}
 
 	if (page_zip_level_var != NULL) {
-		page_zip_level = strtoul(page_zip_level_var, &endptr, 10);
+		page_zip_level = static_cast<uint>(strtoul(page_zip_level_var,
+							   &endptr, 10));
 		ut_ad(*endptr == 0);
 	}
 
diff --git a/extra/mariabackup/crc/crc-intel-pclmul.c b/extra/mariabackup/crc/crc-intel-pclmul.c
index cf4f3ef4380..032802c1823 100644
--- a/extra/mariabackup/crc/crc-intel-pclmul.c
+++ b/extra/mariabackup/crc/crc-intel-pclmul.c
@@ -358,7 +358,7 @@ crc32_reflected_less_than_16 (u32 *pcrc, const byte *inbuf, size_t inlen,
       else
 	{
 	  data = ((const struct u16_unaligned_s *)inbuf)->a;
-	  data |= inbuf[2] << 16;
+	  data |= ((u32) inbuf[2]) << 16;
 	  data ^= crc;
 	  data <<= 8;
 	  crc >>= 24;
diff --git a/extra/mariabackup/xtrabackup.cc b/extra/mariabackup/xtrabackup.cc
index aac87c61742..f3f216226aa 100644
--- a/extra/mariabackup/xtrabackup.cc
+++ b/extra/mariabackup/xtrabackup.cc
@@ -242,11 +242,6 @@ static char*	innobase_ignored_opt;
 char*	innobase_data_home_dir;
 char*	innobase_data_file_path;
 
-my_bool innobase_use_doublewrite;
-my_bool	innobase_file_per_table;
-my_bool innobase_rollback_on_timeout;
-my_bool innobase_create_status_file;
-
 /* The following counter is used to convey information to InnoDB
 about server activity: in selects it is not sensible to call
 srv_active_wake_master_thread after each fetch or search, we only do
@@ -1236,8 +1231,8 @@ struct my_option xb_server_options[] =
    &innobase_data_home_dir, 0, GET_STR, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
   {"innodb_doublewrite", OPT_INNODB_DOUBLEWRITE,
    "Enable InnoDB doublewrite buffer during --prepare.",
-   (G_PTR*) &innobase_use_doublewrite,
-   (G_PTR*) &innobase_use_doublewrite, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
+   (G_PTR*) &srv_use_doublewrite_buf,
+   (G_PTR*) &srv_use_doublewrite_buf, 0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},
   {"innodb_io_capacity", OPT_INNODB_IO_CAPACITY,
    "Number of IOPs the server can do. Tunes the background IO rate",
    (G_PTR*) &srv_io_capacity, (G_PTR*) &srv_io_capacity,
@@ -1256,8 +1251,8 @@ struct my_option xb_server_options[] =
    1, 0},
   {"innodb_file_per_table", OPT_INNODB_FILE_PER_TABLE,
    "Stores each InnoDB table to an .ibd file in the database dir.",
-   (G_PTR*) &innobase_file_per_table,
-   (G_PTR*) &innobase_file_per_table, 0, GET_BOOL, NO_ARG,
+   (G_PTR*) &srv_file_per_table,
+   (G_PTR*) &srv_file_per_table, 0, GET_BOOL, NO_ARG,
    FALSE, 0, 0, 0, 0, 0},
 
   {"innodb_flush_method", OPT_INNODB_FLUSH_METHOD,
@@ -1528,9 +1523,9 @@ static int prepare_export()
   outf= popen(cmdline,"r");
   if (!outf)
     goto end;
-  
+
   char outline[FN_REFLEN];
-  while(fgets(outline, sizeof(outline)-1, outf))
+  while (fgets(outline, FN_REFLEN - 1, outf))
     fprintf(stderr,"%s",outline);
 
   err = pclose(outf);
@@ -1887,14 +1882,7 @@ static bool innodb_init_param()
 	srv_n_read_io_threads = (ulint) innobase_read_io_threads;
 	srv_n_write_io_threads = (ulint) innobase_write_io_threads;
 
-	srv_use_doublewrite_buf = (ibool) innobase_use_doublewrite;
-
-	row_rollback_on_timeout = (ibool) innobase_rollback_on_timeout;
-
-	srv_file_per_table = (my_bool) innobase_file_per_table;
-
 	srv_max_n_open_files = ULINT_UNDEFINED - 5;
-	srv_innodb_status = (ibool) innobase_create_status_file;
 
 	srv_print_verbose_log = verbose ? 2 : 1;
 
@@ -2770,7 +2758,7 @@ static os_thread_ret_t DECLARE_THREAD(log_copying_thread)(void*)
 	for (;;) {
 		os_event_reset(log_copying_stop);
 		os_event_wait_time_low(log_copying_stop,
-				       xtrabackup_log_copy_interval * 1000ULL,
+				       xtrabackup_log_copy_interval * 1000U,
 				       0);
 		if (xtrabackup_copy_logfile()) {
 			break;
@@ -3764,26 +3752,23 @@ xb_filters_free()
 	}
 }
 
-/***********************************************************************
+#ifdef RLIMIT_NOFILE
+/**
 Set the open files limit. Based on set_max_open_files().
-
+@param max_file_limit  requested open files limit
 @return the resulting open files limit. May be less or more than the requested
 value.  */
-static uint
-xb_set_max_open_files(
-/*==================*/
-	uint max_file_limit)	/*!<in: open files limit */
+static ulong xb_set_max_open_files(rlim_t max_file_limit)
 {
-#if defined(RLIMIT_NOFILE)
 	struct rlimit rlimit;
-	uint old_cur;
+	rlim_t old_cur;
 
 	if (getrlimit(RLIMIT_NOFILE, &rlimit)) {
 
 		goto end;
 	}
 
-	old_cur = (uint) rlimit.rlim_cur;
+	old_cur = rlimit.rlim_cur;
 
 	if (rlimit.rlim_cur == RLIM_INFINITY) {
 
@@ -3799,8 +3784,8 @@ xb_set_max_open_files(
 	rlimit.rlim_cur = rlimit.rlim_max = max_file_limit;
 
 	if (setrlimit(RLIMIT_NOFILE, &rlimit)) {
-
-		max_file_limit = old_cur;	/* Use original value */
+		/* Use original value */
+		max_file_limit = static_cast<ulong>(old_cur);
 	} else {
 
 		rlimit.rlim_cur = 0;	/* Safety if next call fails */
@@ -3810,16 +3795,16 @@ xb_set_max_open_files(
 		if (rlimit.rlim_cur) {
 
 			/* If call didn't fail */
-			max_file_limit = (uint) rlimit.rlim_cur;
+			max_file_limit = rlimit.rlim_cur;
 		}
 	}
 
 end:
-	return(max_file_limit);
+	return static_cast<ulong>(max_file_limit);
+}
 #else
-	return(0);
+# define xb_set_max_open_files(x) 0
 #endif
-}
 
 static void stop_backup_threads()
 {
@@ -3950,8 +3935,8 @@ static bool xtrabackup_backup_func()
 	}
 	msg("cd to %s", mysql_real_data_home);
 	encryption_plugin_backup_init(mysql_connection);
-	msg("open files limit requested %u, set to %u",
-	    (uint) xb_open_files_limit,
+	msg("open files limit requested %lu, set to %lu",
+	    xb_open_files_limit,
 	    xb_set_max_open_files(xb_open_files_limit));
 
 	mysql_data_home= mysql_data_home_buff;
@@ -4515,10 +4500,11 @@ xb_space_create_file(
 		fprintf(stderr, "zip_size = " ULINTPF "\n", zip_size);
 
 #ifdef UNIV_DEBUG
-		page_zip.m_start =
+		page_zip.m_start = 0;
 #endif /* UNIV_DEBUG */
-			page_zip.m_end = page_zip.m_nonempty =
-			page_zip.n_blobs = 0;
+		page_zip.m_end = 0;
+		page_zip.m_nonempty = 0;
+		page_zip.n_blobs = 0;
 
 		buf_flush_init_for_writing(NULL, page, &page_zip, false);
 
@@ -6197,10 +6183,10 @@ static int main_low(char** argv)
 		    incremental_lsn);
 	}
 
-	if (xtrabackup_export && innobase_file_per_table == FALSE) {
+	if (xtrabackup_export && !srv_file_per_table) {
 		msg("mariabackup: auto-enabling --innodb-file-per-table due to "
 		    "the --export option");
-		innobase_file_per_table = TRUE;
+		srv_file_per_table = TRUE;
 	}
 
 	/* cannot execute both for now */