Re: new module 'sigsegv'

[Dmitry V. Levin]

On Sun, May 16, 2021 at 07:01:45PM +0200, Bruno Haible wrote:
[...]
> To fix this problem, I'm adding a module 'sigsegv'.

I've tried to rebuild the latest GNU grep with the latest gnulib
and got a few build issues:

sigsegv.c: In function 'sigsegv_handler':
sigsegv.c:1059:36: error: declaration of 'sig' shadows a parameter 
[-Werror=shadow]
 1059 |           SIGSEGV_FOR_ALL_SIGNALS (sig, signal (sig, SIG_DFL);)
      |                                    ^~~
sigsegv.c:738:11: note: in definition of macro 'SIGSEGV_FOR_ALL_SIGNALS'
  738 |     { int var; var = SIGSEGV; { body } }
      |           ^~~
sigsegv.c:64:45: note: shadowed declaration is here
   64 | # define SIGSEGV_FAULT_HANDLER_ARGLIST  int sig, siginfo_t *sip, void 
*ucp
      |                                         ~~~~^~~
sigsegv.c:915:18: note: in expansion of macro 'SIGSEGV_FAULT_HANDLER_ARGLIST'
  915 | sigsegv_handler (SIGSEGV_FAULT_HANDLER_ARGLIST)
      |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

test-sigsegv-catch-segv1.c:42:1: error: no previous prototype for 'handler' 
[-Werror=missing-prototypes]
   42 | handler (void *fault_address, int serious)
      | ^~~~~~~
test-sigsegv-catch-segv1.c:56:1: error: no previous prototype for 'crasher' 
[-Werror=missing-prototypes]
   56 | crasher (uintptr_t p)
      | ^~~~~~~

test-sigsegv-catch-segv2.c:61:1: error: no previous prototype for 'handler' 
[-Werror=missing-prototypes]
   61 | handler (void *fault_address, int serious)
      | ^~~~~~~
test-sigsegv-catch-segv2.c:76:1: error: no previous prototype for 'crasher' 
[-Werror=missing-prototypes]
   76 | crasher (uintptr_t p)
      | ^~~~~~~

test-sigsegv-catch-stackoverflow1.c:62:1: error: no previous prototype for 
'stackoverflow_handler' [-Werror=missing-prototypes]
   62 | stackoverflow_handler (int emergency, stackoverflow_context_t scp)
      | ^~~~~~~~~~~~~~~~~~~~~
test-sigsegv-catch-stackoverflow1.c:76:1: error: no previous prototype for 
'recurse_1' [-Werror=missing-prototypes]
   76 | recurse_1 (int n, volatile int *p)
      | ^~~~~~~~~
test-sigsegv-catch-stackoverflow1.c:84:1: error: no previous prototype for 
'recurse' [-Werror=missing-prototypes]
   84 | recurse (volatile int n)
      | ^~~~~~~

test-sigsegv-catch-stackoverflow2.c:62:1: error: no previous prototype for 
'stackoverflow_handler' [-Werror=missing-prototypes]
   62 | stackoverflow_handler (int emergency, stackoverflow_context_t scp)
      | ^~~~~~~~~~~~~~~~~~~~~
test-sigsegv-catch-stackoverflow2.c:78:1: error: no previous prototype for 
'sigsegv_handler' [-Werror=missing-prototypes]
   78 | sigsegv_handler (void *address, int emergency)
      | ^~~~~~~~~~~~~~~
test-sigsegv-catch-stackoverflow2.c:98:1: error: no previous prototype for 
'recurse_1' [-Werror=missing-prototypes]
   98 | recurse_1 (int n, volatile int *p)
      | ^~~~~~~~~
test-sigsegv-catch-stackoverflow2.c:106:1: error: no previous prototype for 
'recurse' [-Werror=missing-prototypes]
  106 | recurse (volatile int n)
      | ^~~~~~~
test-sigsegv-catch-stackoverflow2.c: In function 'main':
test-sigsegv-catch-stackoverflow2.c:186:27: error: null pointer dereference 
[-Werror=null-dereference]
  186 |       *(volatile int *) 0 = 42;
      |       ~~~~~~~~~~~~~~~~~~~~^~~~

The following gnulib patch makes the compiler happy again:

diff --git a/lib/sigsegv.c b/lib/sigsegv.c
index 312f132b8..b0b406685 100644
--- a/lib/sigsegv.c
+++ b/lib/sigsegv.c
@@ -1056,7 +1056,7 @@ sigsegv_handler (SIGSEGV_FAULT_HANDLER_ARGLIST)
           /* Handler declined responsibility for real.  */
 
           /* Remove ourselves and dump core.  */
-          SIGSEGV_FOR_ALL_SIGNALS (sig, signal (sig, SIG_DFL);)
+          SIGSEGV_FOR_ALL_SIGNALS (signo, signal (signo, SIG_DFL);)
         }
 
 # if HAVE_STACK_OVERFLOW_RECOVERY
diff --git a/tests/test-sigsegv-catch-segv1.c b/tests/test-sigsegv-catch-segv1.c
index 62eef69c8..741a37878 100644
--- a/tests/test-sigsegv-catch-segv1.c
+++ b/tests/test-sigsegv-catch-segv1.c
@@ -38,7 +38,7 @@ uintptr_t page;
 
 volatile int handler_called = 0;
 
-int
+static int
 handler (void *fault_address, int serious)
 {
   handler_called++;
@@ -52,7 +52,7 @@ handler (void *fault_address, int serious)
   return 0;
 }
 
-void
+static void
 crasher (uintptr_t p)
 {
   *(volatile int *) (p + 0x678) = 42;
diff --git a/tests/test-sigsegv-catch-segv2.c b/tests/test-sigsegv-catch-segv2.c
index dd28517f9..f28cb0a8e 100644
--- a/tests/test-sigsegv-catch-segv2.c
+++ b/tests/test-sigsegv-catch-segv2.c
@@ -57,7 +57,7 @@ handler_continuation (void *arg1, void *arg2, void *arg3)
   longjmp (mainloop, pass);
 }
 
-int
+static int
 handler (void *fault_address, int serious)
 {
   handler_called++;
@@ -72,7 +72,7 @@ handler (void *fault_address, int serious)
   return sigsegv_leave_handler (handler_continuation, NULL, NULL, NULL);
 }
 
-void
+static void
 crasher (uintptr_t p)
 {
   *(volatile int *) (p + 0x678 + 8 * pass) = 42;
diff --git a/tests/test-sigsegv-catch-stackoverflow1.c 
b/tests/test-sigsegv-catch-stackoverflow1.c
index c828ed282..bfa04ae8b 100644
--- a/tests/test-sigsegv-catch-stackoverflow1.c
+++ b/tests/test-sigsegv-catch-stackoverflow1.c
@@ -58,7 +58,7 @@ stackoverflow_handler_continuation (void *arg1, void *arg2, 
void *arg3)
   longjmp (mainloop, arg);
 }
 
-void
+static void
 stackoverflow_handler (int emergency, stackoverflow_context_t scp)
 {
   char dummy;
@@ -72,7 +72,7 @@ stackoverflow_handler (int emergency, stackoverflow_context_t 
scp)
                          (void *) (long) (emergency ? -1 : pass), NULL, NULL);
 }
 
-volatile int *
+static volatile int *
 recurse_1 (int n, volatile int *p)
 {
   if (n < INT_MAX)
@@ -80,7 +80,7 @@ recurse_1 (int n, volatile int *p)
   return p;
 }
 
-int
+static int
 recurse (volatile int n)
 {
   return *recurse_1 (n, &n);
diff --git a/tests/test-sigsegv-catch-stackoverflow2.c 
b/tests/test-sigsegv-catch-stackoverflow2.c
index b94d1310b..f7fd191a6 100644
--- a/tests/test-sigsegv-catch-stackoverflow2.c
+++ b/tests/test-sigsegv-catch-stackoverflow2.c
@@ -58,7 +58,7 @@ stackoverflow_handler_continuation (void *arg1, void *arg2, 
void *arg3)
   longjmp (mainloop, arg);
 }
 
-void
+static void
 stackoverflow_handler (int emergency, stackoverflow_context_t scp)
 {
   pass++;
@@ -74,7 +74,7 @@ stackoverflow_handler (int emergency, stackoverflow_context_t 
scp)
                          (void *) (long) (emergency ? -1 : pass), NULL, NULL);
 }
 
-int
+static int
 sigsegv_handler (void *address, int emergency)
 {
   /* This test is necessary to distinguish stack overflow and SIGSEGV.  */
@@ -94,7 +94,7 @@ sigsegv_handler (void *address, int emergency)
                                 (void *) (long) pass, NULL, NULL);
 }
 
-volatile int *
+static volatile int *
 recurse_1 (int n, volatile int *p)
 {
   if (n < INT_MAX)
@@ -102,7 +102,7 @@ recurse_1 (int n, volatile int *p)
   return p;
 }
 
-int
+static int
 recurse (volatile int n)
 {
   return *recurse_1 (n, &n);
@@ -183,6 +183,9 @@ main ()
       *(volatile int *) (page + 0x678) = 42;
       break;
     case 3:
+#if 6 < __GNUC__
+# pragma GCC diagnostic ignored "-Wnull-dereference"
+#endif
       *(volatile int *) 0 = 42;
       break;
     case 4:

-- 
ldv