Fix const qualifier build errors with recent glibc

A recent change in glibc 2.42.9000 [1] changes the return type of
strstr() and other string functions to be 'const char *' when the
input is a 'const char *'.

This breaks the build in various files with errors such as :

  error: initialization discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
    208 |         char *pidstr = strstr(filename, "%");
        |                        ^~~~~~

Fix this by changing the type of the variables that store the result
of these functions to 'const char *'.

[1] https://sourceware.org/git/?p=glibc.git;a=commit;h=cd748a63ab1a7ae846175c532a3daab341c62690

Signed-off-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20251209174328.698774-1-clg@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

backends/tpm/tpm_passthrough.c

@@ -211,7 +211,7 @@ static size_t tpm_passthrough_get_buffer_size(TPMBackend *tb)
 static int tpm_passthrough_open_sysfs_cancel(TPMPassthruState *tpm_pt)
 {
     int fd = -1;
-    char *dev;
+    const char *dev;
     char path[PATH_MAX];
 
     if (tpm_pt->options->cancel_path) {

block/vmdk.c

@@ -1089,7 +1089,7 @@ vmdk_open_vmdk4(BlockDriverState *bs, BdrvChild *file, int flags,
 static int vmdk_parse_description(const char *desc, const char *opt_name,
         char *buf, int buf_size)
 {
-    char *opt_pos, *opt_end;
+    const char *opt_pos, *opt_end;
     const char *end = desc + strlen(desc);
 
     opt_pos = strstr(desc, opt_name);

block/vvfat.c

@@ -1826,7 +1826,7 @@ cluster_was_modified(BDRVVVFATState *s, uint32_t cluster_num)
 
 static const char* get_basename(const char* path)
 {
-    char* basename = strrchr(path, '/');
+    const char *basename = strrchr(path, '/');
     if (basename == NULL)
         return path;
     else

gdbstub/gdbstub.c

@@ -362,7 +362,7 @@ static const char *get_feature_xml(const char *p, const char **newp,
      * qXfer:features:read:ANNEX:OFFSET,LENGTH'
      *                     ^p    ^newp
      */
-    char *term = strchr(p, ':');
+    const char *term = strchr(p, ':');
     *newp = term + 1;
     len = term - p;
 

qga/commands-linux.c

@@ -403,7 +403,8 @@ static bool build_guest_fsinfo_for_pci_dev(char const *syspath,
     int i, offset, nhosts = 0, pcilen;
     GuestPCIAddress *pciaddr = disk->pci_controller;
     bool has_ata = false, has_host = false, has_tgt = false;
-    char *p, *driver = NULL;
+    const char *p;
+    char *driver = NULL;
     bool ret = false;
 
     p = strstr(syspath, "/devices/pci");
@@ -543,7 +544,7 @@ static bool build_guest_fsinfo_for_nonpci_virtio(char const *syspath,
                                                  Error **errp)
 {
     unsigned int tgt[3];
-    char *p;
+    const char *p;
 
     if (!strstr(syspath, "/virtio") || !strstr(syspath, "/block")) {
         g_debug("Unsupported virtio device '%s'", syspath);
@@ -575,7 +576,7 @@ static bool build_guest_fsinfo_for_ccw_dev(char const *syspath,
                                            Error **errp)
 {
     unsigned int cssid, ssid, subchno, devno;
-    char *p;
+    const char *p;
 
     p = strstr(syspath, "/devices/css");
     if (!p || sscanf(p + 12, "%*x/%x.%x.%x/%*x.%*x.%x/",

ui/ui-hmp-cmds.c

@@ -418,7 +418,7 @@ err_out:
 void sendkey_completion(ReadLineState *rs, int nb_args, const char *str)
 {
     int i;
-    char *sep;
+    const char *sep;
     size_t len;
 
     if (nb_args != 2) {

util/log.c

@@ -203,7 +203,7 @@ static ValidFilenameTemplateResult
 valid_filename_template(const char *filename, bool per_thread, Error **errp)
 {
     if (filename) {
-        char *pidstr = strstr(filename, "%");
+        const char *pidstr = strstr(filename, "%");
 
         if (pidstr) {
             /* We only accept one %d, no other format strings */