stdio-common: Suppress Clang warnings on scanf13.c with fortify enable

clang-19 shows:

scanf13.c:28:40: error: 'sscanf' may overflow; destination buffer in argument 4 has size 8, but the corresponding specifier may require size 11 [-Werror,-Wfortify-source]
   28 |               "A%ms%10ms%4m[bcd]%4mcB", &sp1, &sp2, &sp3, &sp4) != 4)
      |                                               ^
scanf13.c:94:34: error: 'sscanf' may overflow; destination buffer in argument 3 has size 8, but the corresponding specifier may require size 2049 [-Werror,-Wfortify-source]
   94 |   if (sscanf (buf, "%2048ms%mc", &sp3, &sp4) != 2)
      |                                  ^
scanf13.c:110:61: error: 'sscanf' may overflow; destination buffer in argument 4 has size 8, but the corresponding specifier may require size 1501 [-Werror,-Wfortify-source]
  110 |   if (sscanf (buf, "%4mc%1500m[dr/]%548m[abc/d]%3mc", &sp1, &sp2, &sp3, &sp4)
      |                                                             ^
scanf13.c:110:67: error: 'sscanf' may overflow; destination buffer in argument 5 has size 8, but the corresponding specifier may require size 549 [-Werror,-Wfortify-source]
  110 |   if (sscanf (buf, "%4mc%1500m[dr/]%548m[abc/d]%3mc", &sp1, &sp2, &sp3, &sp4)

clang does have some support to handle 'm' prefix for -Wformat; but it
lacks support for -Wfortify to understand that it is up to libc to
allocate the memory, and uses the pointer size instead to calculate
validity.

diff --git a/stdio-common/scanf13.c b/stdio-common/scanf13.c
index 65b14297206ec151cc7a958f2a3e9578d7d61a50..131abb33def8e1d147fef7a723df6cdaca6a536d 100644 (file)
--- a/stdio-common/scanf13.c
+++ b/stdio-common/scanf13.c
@@ -24,6 +24,7 @@ main (void)
   DIAG_PUSH_NEEDS_COMMENT_CLANG;
   DIAG_IGNORE_NEEDS_COMMENT_CLANG (13, "-Wformat-invalid-specifier");
   DIAG_IGNORE_NEEDS_COMMENT_CLANG (13, "-Wformat-extra-args");
+  DIAG_IGNORE_NEEDS_COMMENT_CLANG (13, "-Wfortify-source");
   if (sscanf ("A  \xc3\x84-\t\t\xc3\x84-abcdefbcd\t\xc3\x84-B",
              "A%ms%10ms%4m[bcd]%4mcB", &sp1, &sp2, &sp3, &sp4) != 4)
     FAIL ();
@@ -91,6 +92,8 @@ main (void)
        FAIL ();
       free (sp2);
     }
+  DIAG_PUSH_NEEDS_COMMENT_CLANG;
+  DIAG_IGNORE_NEEDS_COMMENT_CLANG (13, "-Wfortify-source");
   if (sscanf (buf, "%2048ms%mc", &sp3, &sp4) != 2)
     FAIL ();
   else
@@ -131,6 +134,7 @@ main (void)
        FAIL ();
       free (sp4);
     }
+  DIAG_POP_NEEDS_COMMENT_CLANG;
   if (sscanf (buf, "%mS%mC", &lsp1, &lsp2) != 2)
     FAIL ();
   else
@@ -150,6 +154,7 @@ main (void)
   DIAG_PUSH_NEEDS_COMMENT_CLANG;
   DIAG_IGNORE_NEEDS_COMMENT_CLANG (13, "-Wformat-invalid-specifier");
   DIAG_IGNORE_NEEDS_COMMENT_CLANG (13, "-Wformat-extra-args");
+  DIAG_IGNORE_NEEDS_COMMENT_CLANG (13, "-Wfortify-source");
   if (sscanf (buf, "%2048mls%mlc", &lsp3, &lsp4) != 2)
     FAIL ();
   else