From: Akihiko Odaki <akihiko.odaki@daynix.com>

romsize is an uint32_t variable. Specifying -1 as an uint32_t value is
obscure way to denote UINT32_MAX.

Worse, if int is wider than 32-bit, it will change the behavior of a
construct like the following:
romsize = -1;
if (romsize != -1) {
    ...
}

When -1 is assigned to romsize, -1 will be implicitly casted into
uint32_t, resulting in UINT32_MAX. On contrary, when evaluating
romsize != -1, romsize will be casted into int, and it will be a
comparison of UINT32_MAX and -1, and result in false.

Replace -1 with UINT32_MAX for statements involving the variable to
clarify the intent and prevent potential breakage.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20240627-reuse-v10-10-7ca0b8ed3d9f@daynix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/pci/pci.c             | 8 ++++----
 hw/xen/xen_pt_load_rom.c | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index fa85f87b1c..4c7be52951 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -70,7 +70,7 @@ static bool pcie_has_upstream_port(PCIDevice *dev);
 static Property pci_props[] = {
     DEFINE_PROP_PCI_DEVFN("addr", PCIDevice, devfn, -1),
     DEFINE_PROP_STRING("romfile", PCIDevice, romfile),
-    DEFINE_PROP_UINT32("romsize", PCIDevice, romsize, -1),
+    DEFINE_PROP_UINT32("romsize", PCIDevice, romsize, UINT32_MAX),
     DEFINE_PROP_UINT32("rombar",  PCIDevice, rom_bar, 1),
     DEFINE_PROP_BIT("multifunction", PCIDevice, cap_present,
                     QEMU_PCI_CAP_MULTIFUNCTION_BITNR, false),
@@ -2073,7 +2073,7 @@ static void pci_qdev_realize(DeviceState *qdev, Error **errp)
                                  g_cmp_uint32, NULL);
     }
 
-    if (pci_dev->romsize != -1 && !is_power_of_2(pci_dev->romsize)) {
+    if (pci_dev->romsize != UINT32_MAX && !is_power_of_2(pci_dev->romsize)) {
         error_setg(errp, "ROM size %u is not a power of two", pci_dev->romsize);
         return;
     }
@@ -2359,7 +2359,7 @@ static void pci_add_option_rom(PCIDevice *pdev, bool is_default_rom,
         return;
     }
 
-    if (load_file || pdev->romsize == -1) {
+    if (load_file || pdev->romsize == UINT32_MAX) {
         path = qemu_find_file(QEMU_FILE_TYPE_BIOS, pdev->romfile);
         if (path == NULL) {
             path = g_strdup(pdev->romfile);
@@ -2378,7 +2378,7 @@ static void pci_add_option_rom(PCIDevice *pdev, bool is_default_rom,
                        pdev->romfile);
             return;
         }
-        if (pdev->romsize != -1) {
+        if (pdev->romsize != UINT_MAX) {
             if (size > pdev->romsize) {
                 error_setg(errp, "romfile \"%s\" (%u bytes) "
                            "is too large for ROM size %u",
diff --git a/hw/xen/xen_pt_load_rom.c b/hw/xen/xen_pt_load_rom.c
index 03422a8a71..6bc64acd33 100644
--- a/hw/xen/xen_pt_load_rom.c
+++ b/hw/xen/xen_pt_load_rom.c
@@ -53,7 +53,7 @@ void *pci_assign_dev_load_option_rom(PCIDevice *dev,
     }
     fseek(fp, 0, SEEK_SET);
 
-    if (dev->romsize != -1) {
+    if (dev->romsize != UINT_MAX) {
         if (st.st_size > dev->romsize) {
             error_report("ROM BAR \"%s\" (%ld bytes) is too large for ROM size %u",
                          rom_file, (long) st.st_size, dev->romsize);
-- 
MST