[PATCH v2 0/4] Fix const qualifier build errors with recent glibc

[PATCH v2 0/4] Fix const qualifier build errors with recent glibc

[Cédric Le Goater]

Hello,

More fixes for the build breakage due to the recent change in glibc
2.42.9000 : 

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

Thanks,

C. 

Changes in v2:

 - I did a full QEMU build this time and found a couple more issues to
   fix. We should be done now.

Cédric Le Goater (4):
  i386: Fix const qualifier build errors with recent glibc
  tests/vhost-user-bridge.c: Fix const qualifier build errors with
    recent glibc
  monitor: Fix const qualifier build errors with recent glibc
  gdbstub: Fix const qualifier build errors with recent glibc

 gdbstub/user.c            |  2 +-
 hw/i386/x86-common.c      |  2 +-
 monitor/hmp.c             |  5 +++--
 tests/vhost-user-bridge.c | 10 ++++------
 4 files changed, 9 insertions(+), 10 deletions(-)

-- 
2.52.0

[PATCH v2 1/4] i386: Fix const qualifier build errors with recent glibc

[Cédric Le Goater]

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 :

  ../hw/i386/x86-common.c:827:11: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
  827 |     vmode = strstr(kernel_cmdline, "vga=");
      |           ^

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

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Link: https://lore.kernel.org/qemu-devel/20251210181306.926334-2-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 hw/i386/x86-common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/i386/x86-common.c b/hw/i386/x86-common.c
index c844749900a30c9c9c284c529e93c84c9457b128..f77e2e63046ff56d079363e411a9ee0eca365291 100644
--- a/hw/i386/x86-common.c
+++ b/hw/i386/x86-common.c
@@ -654,7 +654,7 @@ void x86_load_linux(X86MachineState *x86ms,
     uint8_t header[8192], *setup, *kernel;
     hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0;
     FILE *f;
-    char *vmode;
+    const char *vmode;
     MachineState *machine = MACHINE(x86ms);
     struct setup_data *setup_data;
     const char *kernel_filename = machine->kernel_filename;
-- 
2.52.0

[PATCH v2 2/4] tests/vhost-user-bridge.c: Fix const qualifier build errors with recent glibc

[Cédric Le Goater]

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 :

../tests/vhost-user-bridge.c: In function ‘vubr_parse_host_port’:
../tests/vhost-user-bridge.c:749:15: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
  749 |     char *p = strchr(buf, ':');
      |               ^~~~~~

Fix this by using the glib g_strsplit() routine instead of strdup().

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

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Yodel Eldar <yodel.eldar@yodel.dev>
Tested-by: Yodel Eldar <yodel.eldar@yodel.dev>
Link: https://lore.kernel.org/qemu-devel/20251210181306.926334-3-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 tests/vhost-user-bridge.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
index a5c711b1de8e9c164dd1614f4329b8e3c05d0402..ce4c3426d3938a0b54195f3e95bb1f1c3c4ae823 100644
--- a/tests/vhost-user-bridge.c
+++ b/tests/vhost-user-bridge.c
@@ -746,14 +746,12 @@ vubr_run(VubrDev *dev)
 static int
 vubr_parse_host_port(const char **host, const char **port, const char *buf)
 {
-    char *p = strchr(buf, ':');
-
-    if (!p) {
+    g_auto(GStrv) tokens = g_strsplit(buf, ":", 2);
+    if (!tokens[0] || !tokens[1]) {
         return -1;
     }
-    *p = '\0';
-    *host = strdup(buf);
-    *port = strdup(p + 1);
+    *host = g_steal_pointer(&tokens[0]);
+    *port = g_steal_pointer(&tokens[1]);
     return 0;
 }
 
-- 
2.52.0

[PATCH v2 3/4] monitor: Fix const qualifier build errors with recent glibc

[Cédric Le Goater]

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

../monitor/hmp.c:589:7: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
  589 |     p = strchr(type, ':');
      |       ^

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>
---
 monitor/hmp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/monitor/hmp.c b/monitor/hmp.c
index 34e2b8f748b425e1e4446e8e64aa25b1433d1162..a3ee02e52cda530508b170c4c5e8357b304f7df6 100644
--- a/monitor/hmp.c
+++ b/monitor/hmp.c
@@ -577,10 +577,11 @@ static const char *get_command_name(const char *cmdline,
  * Read key of 'type' into 'key' and return the current
  * 'type' pointer.
  */
-static char *key_get_info(const char *type, char **key)
+static const char *key_get_info(const char *type, char **key)
 {
     size_t len;
-    char *p, *str;
+    const char *p;
+    char *str;
 
     if (*type == ',') {
         type++;
-- 
2.52.0

[PATCH v2 4/4] gdbstub: Fix const qualifier build errors with recent glibc

[Cédric Le Goater]

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 :

../gdbstub/user.c:322:21: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
  322 |     pid_placeholder = strstr(path, "%d");
      |                     ^
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>
---
 gdbstub/user.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gdbstub/user.c b/gdbstub/user.c
index 2e14ded3f01053d4d4a36426c509ce7a6b81cb67..e233c598165ca1b10a5f2a89c87136df9af636ca 100644
--- a/gdbstub/user.c
+++ b/gdbstub/user.c
@@ -317,7 +317,7 @@ static bool gdb_accept_socket(int gdb_fd)
 static int gdbserver_open_socket(const char *path, Error **errp)
 {
     g_autoptr(GString) buf = g_string_new("");
-    char *pid_placeholder;
+    const char *pid_placeholder;
 
     pid_placeholder = strstr(path, "%d");
     if (pid_placeholder != NULL) {
-- 
2.52.0

Re: [PATCH v2 3/4] monitor: Fix const qualifier build errors with recent glibc

[Philippe Mathieu-Daudé]

On 15/12/25 11:19, Cédric Le Goater wrote:
> A recent change in glibc 2.42.9000 [1] changes the return type of
> strchr() and other string functions to be 'const char *' when the
> input is a 'const char *'. This breaks the build in :
> 
> ../monitor/hmp.c:589:7: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
>    589 |     p = strchr(type, ':');
>        |       ^
> 
> 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>
> ---
>   monitor/hmp.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Re: [PATCH v2 4/4] gdbstub: Fix const qualifier build errors with recent glibc

[Philippe Mathieu-Daudé]

On 15/12/25 11:19, Cédric Le Goater wrote:
> 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 :
> 
> ../gdbstub/user.c:322:21: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
>    322 |     pid_placeholder = strstr(path, "%d");
>        |                     ^
> 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>
> ---
>   gdbstub/user.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Re: [PATCH v2 2/4] tests/vhost-user-bridge.c: Fix const qualifier build errors with recent glibc

[Thomas Huth]

On 15/12/2025 11.19, Cédric Le Goater wrote:
> 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 :
> 
> ../tests/vhost-user-bridge.c: In function ‘vubr_parse_host_port’:
> ../tests/vhost-user-bridge.c:749:15: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
>    749 |     char *p = strchr(buf, ':');
>        |               ^~~~~~
> 
> Fix this by using the glib g_strsplit() routine instead of strdup().
> 
> [1] https://sourceware.org/git/?p=glibc.git;a=commit;h=cd748a63ab1a7ae846175c532a3daab341c62690
> 
> Suggested-by: Peter Maydell <peter.maydell@linaro.org>
> Acked-by: Yodel Eldar <yodel.eldar@yodel.dev>
> Tested-by: Yodel Eldar <yodel.eldar@yodel.dev>
> Link: https://lore.kernel.org/qemu-devel/20251210181306.926334-3-clg@redhat.com
> Signed-off-by: Cédric Le Goater <clg@redhat.com>
> ---
>   tests/vhost-user-bridge.c | 10 ++++------
>   1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
> index a5c711b1de8e9c164dd1614f4329b8e3c05d0402..ce4c3426d3938a0b54195f3e95bb1f1c3c4ae823 100644
> --- a/tests/vhost-user-bridge.c
> +++ b/tests/vhost-user-bridge.c
> @@ -746,14 +746,12 @@ vubr_run(VubrDev *dev)
>   static int
>   vubr_parse_host_port(const char **host, const char **port, const char *buf)
>   {
> -    char *p = strchr(buf, ':');
> -
> -    if (!p) {
> +    g_auto(GStrv) tokens = g_strsplit(buf, ":", 2);
> +    if (!tokens[0] || !tokens[1]) {
>           return -1;
>       }
> -    *p = '\0';
> -    *host = strdup(buf);
> -    *port = strdup(p + 1);
> +    *host = g_steal_pointer(&tokens[0]);
> +    *port = g_steal_pointer(&tokens[1]);
>       return 0;
>   }
>   

Reviewed-by: Thomas Huth <thuth@redhat.com>

Re: [PATCH v2 3/4] monitor: Fix const qualifier build errors with recent glibc

[Thomas Huth]

On 15/12/2025 11.19, Cédric Le Goater wrote:
> A recent change in glibc 2.42.9000 [1] changes the return type of
> strchr() and other string functions to be 'const char *' when the
> input is a 'const char *'. This breaks the build in :
> 
> ../monitor/hmp.c:589:7: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
>    589 |     p = strchr(type, ':');
>        |       ^
> 
> 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>
> ---
>   monitor/hmp.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/monitor/hmp.c b/monitor/hmp.c
> index 34e2b8f748b425e1e4446e8e64aa25b1433d1162..a3ee02e52cda530508b170c4c5e8357b304f7df6 100644
> --- a/monitor/hmp.c
> +++ b/monitor/hmp.c
> @@ -577,10 +577,11 @@ static const char *get_command_name(const char *cmdline,
>    * Read key of 'type' into 'key' and return the current
>    * 'type' pointer.
>    */
> -static char *key_get_info(const char *type, char **key)
> +static const char *key_get_info(const char *type, char **key)
>   {
>       size_t len;
> -    char *p, *str;
> +    const char *p;
> +    char *str;
>   
>       if (*type == ',') {
>           type++;

Reviewed-by: Thomas Huth <thuth@redhat.com>

Re: [PATCH v2 4/4] gdbstub: Fix const qualifier build errors with recent glibc

[Thomas Huth]

On 15/12/2025 11.19, Cédric Le Goater wrote:
> 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 :
> 
> ../gdbstub/user.c:322:21: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
>    322 |     pid_placeholder = strstr(path, "%d");
>        |                     ^
> 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>
> ---
>   gdbstub/user.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/gdbstub/user.c b/gdbstub/user.c
> index 2e14ded3f01053d4d4a36426c509ce7a6b81cb67..e233c598165ca1b10a5f2a89c87136df9af636ca 100644
> --- a/gdbstub/user.c
> +++ b/gdbstub/user.c
> @@ -317,7 +317,7 @@ static bool gdb_accept_socket(int gdb_fd)
>   static int gdbserver_open_socket(const char *path, Error **errp)
>   {
>       g_autoptr(GString) buf = g_string_new("");
> -    char *pid_placeholder;
> +    const char *pid_placeholder;
>   
>       pid_placeholder = strstr(path, "%d");
>       if (pid_placeholder != NULL) {

Reviewed-by: Thomas Huth <thuth@redhat.com>