[gcc r13-1802] Fix handling of zero capacity regions in -Wanalyzer-allocation-size [PR106394]

[gcc r13-1802] Fix handling of zero capacity regions in -Wanalyzer-allocation-size [PR106394]

[Tim Lange]

https://gcc.gnu.org/g:b4cc945c045db74f719ab030969806c14e2d5fc3

commit r13-1802-gb4cc945c045db74f719ab030969806c14e2d5fc3
Author: Tim Lange <mail@tim-lange.me>
Date:   Fri Jul 22 21:44:07 2022 +0200

    Fix handling of zero capacity regions in -Wanalyzer-allocation-size [PR106394]
    
    This patch unifies the handling of zero capacity regions for structs
    and other types in the allocation size checker.
    Regression-tested on x86_64 Linux.
    
    2022-07-22  Tim Lange  <mail@tim-lange.me>
    
    gcc/analyzer/ChangeLog:
    
            PR analyzer/106394
            * region-model.cc (capacity_compatible_with_type): Always return true
            if alloc_size is zero.
    
    gcc/testsuite/ChangeLog:
    
            PR analyzer/106394
            * gcc.dg/analyzer/pr106394.c: New test.

Diff:
---
 gcc/analyzer/region-model.cc             |  2 +-
 gcc/testsuite/gcc.dg/analyzer/pr106394.c | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc
index 5bb7112a383..f7df2fca245 100644
--- a/gcc/analyzer/region-model.cc
+++ b/gcc/analyzer/region-model.cc
@@ -2956,7 +2956,7 @@ capacity_compatible_with_type (tree cst, tree pointee_size_tree,
   unsigned HOST_WIDE_INT alloc_size = TREE_INT_CST_LOW (cst);
 
   if (is_struct)
-    return alloc_size >= pointee_size;
+    return alloc_size == 0 || alloc_size >= pointee_size;
   return alloc_size % pointee_size == 0;
 }
 
diff --git a/gcc/testsuite/gcc.dg/analyzer/pr106394.c b/gcc/testsuite/gcc.dg/analyzer/pr106394.c
new file mode 100644
index 00000000000..96bb175fc14
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/pr106394.c
@@ -0,0 +1,19 @@
+struct msm_gpu {
+  // [...snip...]
+  const struct msm_gpu_perfcntr *perfcntrs;
+  // [...snip...]
+};
+
+struct msm_gpu_perfcntr {
+  // [...snip...]
+  const char *name;
+};
+
+static const struct msm_gpu_perfcntr perfcntrs[] = {};
+
+struct msm_gpu *test(struct msm_gpu *gpu) {
+  // [...snip...]
+  gpu->perfcntrs = perfcntrs;
+  // [...snip...]
+  return gpu;
+}