[src/trunk]: src/usr.bin/xlint lint: remove custom memory allocator

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/b64ec91753ae
branches:  trunk
changeset: 373026:b64ec91753ae
user:      rillig <rillig%NetBSD.org@localhost>
date:      Fri Jan 13 19:41:50 2023 +0000

description:
lint: remove custom memory allocator

Besides adding complexity, the custom memory allocator didn't invalidate
freed memory, which made it harder to find possible use-after-free bugs.

diffstat:

 usr.bin/xlint/common/externs.h |    3 +-
 usr.bin/xlint/common/mem.c     |   16 +----
 usr.bin/xlint/lint1/externs1.h |    8 +-
 usr.bin/xlint/lint1/init.c     |    9 +-
 usr.bin/xlint/lint1/lint1.h    |   16 ++++-
 usr.bin/xlint/lint1/main1.c    |    5 +-
 usr.bin/xlint/lint1/mem1.c     |  132 ++++++++++++++++------------------------
 usr.bin/xlint/lint1/tree.c     |    6 +-
 usr.bin/xlint/lint2/externs2.h |    3 +-
 usr.bin/xlint/lint2/main2.c    |    6 +-
 usr.bin/xlint/lint2/mem2.c     |   42 +-----------
 11 files changed, 90 insertions(+), 156 deletions(-)

diffs (truncated from 534 to 300 lines):

diff -r 80e7d55b305a -r b64ec91753ae usr.bin/xlint/common/externs.h
--- a/usr.bin/xlint/common/externs.h    Fri Jan 13 18:43:42 2023 +0000
+++ b/usr.bin/xlint/common/externs.h    Fri Jan 13 19:41:50 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: externs.h,v 1.24 2021/09/04 14:48:27 rillig Exp $      */
+/*     $NetBSD: externs.h,v 1.25 2023/01/13 19:41:50 rillig Exp $      */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -45,7 +45,6 @@
 /*
  * mem.c
  */
-extern size_t  mem_block_size(void);
 extern void    *xmalloc(size_t);
 extern void    *xcalloc(size_t, size_t);
 extern void    *xrealloc(void *, size_t);
diff -r 80e7d55b305a -r b64ec91753ae usr.bin/xlint/common/mem.c
--- a/usr.bin/xlint/common/mem.c        Fri Jan 13 18:43:42 2023 +0000
+++ b/usr.bin/xlint/common/mem.c        Fri Jan 13 19:41:50 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mem.c,v 1.20 2022/05/20 21:18:54 rillig Exp $  */
+/*     $NetBSD: mem.c,v 1.21 2023/01/13 19:41:50 rillig Exp $  */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,27 +37,15 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID)
-__RCSID("$NetBSD: mem.c,v 1.20 2022/05/20 21:18:54 rillig Exp $");
+__RCSID("$NetBSD: mem.c,v 1.21 2023/01/13 19:41:50 rillig Exp $");
 #endif
 
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
-#include <unistd.h>
 
 #include "lint.h"
 
-#if defined(IS_LINT1) || defined(IS_LINT2)
-size_t
-mem_block_size(void)
-{
-       unsigned int pagesize;
-
-       pagesize = (unsigned int)getpagesize();
-       return (MBLKSIZ + pagesize - 1) / pagesize * pagesize;
-}
-#endif
-
 static void *
 not_null(void *ptr)
 {
diff -r 80e7d55b305a -r b64ec91753ae usr.bin/xlint/lint1/externs1.h
--- a/usr.bin/xlint/lint1/externs1.h    Fri Jan 13 18:43:42 2023 +0000
+++ b/usr.bin/xlint/lint1/externs1.h    Fri Jan 13 19:41:50 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: externs1.h,v 1.170 2022/10/01 09:59:40 rillig Exp $    */
+/*     $NetBSD: externs1.h,v 1.171 2023/01/13 19:41:50 rillig Exp $    */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -99,8 +99,6 @@
 extern void    add_directory_replacement(char *);
 extern const char *transform_filename(const char *, size_t);
 
-extern void    initmem(void);
-
 extern void    *block_zero_alloc(size_t);
 extern void    *level_zero_alloc(size_t, size_t);
 extern void    level_free_all(size_t);
@@ -108,8 +106,8 @@
 extern void    *expr_zero_alloc(size_t);
 extern tnode_t *expr_alloc_tnode(void);
 extern void    expr_free_all(void);
-extern struct  memory_block *expr_save_memory(void);
-extern void    expr_restore_memory(struct memory_block *);
+extern memory_pool expr_save_memory(void);
+extern void    expr_restore_memory(memory_pool);
 
 /*
  * debug.c
diff -r 80e7d55b305a -r b64ec91753ae usr.bin/xlint/lint1/init.c
--- a/usr.bin/xlint/lint1/init.c        Fri Jan 13 18:43:42 2023 +0000
+++ b/usr.bin/xlint/lint1/init.c        Fri Jan 13 19:41:50 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: init.c,v 1.237 2022/08/28 12:04:47 rillig Exp $        */
+/*     $NetBSD: init.c,v 1.238 2023/01/13 19:41:50 rillig Exp $        */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -38,7 +38,7 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID)
-__RCSID("$NetBSD: init.c,v 1.237 2022/08/28 12:04:47 rillig Exp $");
+__RCSID("$NetBSD: init.c,v 1.238 2023/01/13 19:41:50 rillig Exp $");
 #endif
 
 #include <stdlib.h>
@@ -309,7 +309,6 @@
        tnode_t *ln;
        type_t *lutp;
        tspec_t lt, rt;
-       struct memory_block *tmem;
 
        lutp = expr_unqualified_type(ltp);
 
@@ -334,9 +333,9 @@
         * Preserve the tree memory. This is necessary because otherwise
         * expr() would free it.
         */
-       tmem = expr_save_memory();
+       memory_pool saved_mem = expr_save_memory();
        expr(rn, true, false, true, false);
-       expr_restore_memory(tmem);
+       expr_restore_memory(saved_mem);
 
        check_bit_field_init(ln, lt, rt);
 
diff -r 80e7d55b305a -r b64ec91753ae usr.bin/xlint/lint1/lint1.h
--- a/usr.bin/xlint/lint1/lint1.h       Fri Jan 13 18:43:42 2023 +0000
+++ b/usr.bin/xlint/lint1/lint1.h       Fri Jan 13 19:41:50 2023 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: lint1.h,v 1.158 2022/10/01 09:42:40 rillig Exp $ */
+/* $NetBSD: lint1.h,v 1.159 2023/01/13 19:41:50 rillig Exp $ */
 
 /*
  * Copyright (c) 1996 Christopher G. Demetriou.  All Rights Reserved.
@@ -36,6 +36,18 @@
 #include "err-msgs.h"
 #include "op.h"
 
+/*
+ * A memory pool collects allocated objects that must be available until:
+ * - the end of a block,
+ * - the end of an expression, or
+ * - the end of the translation unit.
+ */
+typedef struct memory_pool {
+       void    **items;
+       size_t  len;
+       size_t  cap;
+} memory_pool;
+
 /* See saved_lwarn in cgram.y. */
 #define LWARN_ALL      (-2)
 #define LWARN_NONE     (-1)
@@ -426,7 +438,7 @@
        tnode_t *c_switch_expr;
        case_label_t *c_case_labels;    /* list of case values */
 
-       struct  memory_block *c_for_expr3_mem; /* saved memory for end of loop
+       memory_pool c_for_expr3_mem;    /* saved memory for end of loop
                                         * expression in for() */
        tnode_t *c_for_expr3;           /* end of loop expr in for() */
        pos_t   c_for_expr3_pos;        /* position of end of loop expr */
diff -r 80e7d55b305a -r b64ec91753ae usr.bin/xlint/lint1/main1.c
--- a/usr.bin/xlint/lint1/main1.c       Fri Jan 13 18:43:42 2023 +0000
+++ b/usr.bin/xlint/lint1/main1.c       Fri Jan 13 19:41:50 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: main1.c,v 1.65 2022/07/05 22:50:41 rillig Exp $        */
+/*     $NetBSD: main1.c,v 1.66 2023/01/13 19:41:50 rillig Exp $        */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,7 +37,7 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID)
-__RCSID("$NetBSD: main1.c,v 1.65 2022/07/05 22:50:41 rillig Exp $");
+__RCSID("$NetBSD: main1.c,v 1.66 2023/01/13 19:41:50 rillig Exp $");
 #endif
 
 #include <sys/types.h>
@@ -259,7 +259,6 @@
 #endif
 
        (void)signal(SIGFPE, sigfpe);
-       initmem();
        initdecl();
        initscan();
 
diff -r 80e7d55b305a -r b64ec91753ae usr.bin/xlint/lint1/mem1.c
--- a/usr.bin/xlint/lint1/mem1.c        Fri Jan 13 18:43:42 2023 +0000
+++ b/usr.bin/xlint/lint1/mem1.c        Fri Jan 13 19:41:50 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mem1.c,v 1.63 2022/05/20 21:18:55 rillig Exp $ */
+/*     $NetBSD: mem1.c,v 1.64 2023/01/13 19:41:50 rillig Exp $ */
 
 /*
  * Copyright (c) 1994, 1995 Jochen Pohl
@@ -37,7 +37,7 @@
 
 #include <sys/cdefs.h>
 #if defined(__RCSID)
-__RCSID("$NetBSD: mem1.c,v 1.63 2022/05/20 21:18:55 rillig Exp $");
+__RCSID("$NetBSD: mem1.c,v 1.64 2023/01/13 19:41:50 rillig Exp $");
 #endif
 
 #include <sys/param.h>
@@ -160,74 +160,60 @@
        return fn->fn_id;
 }
 
-/*
- * Memory for declarations and other things that must be available
- * until the end of a block (or the end of the translation unit)
- * is associated with the corresponding mem_block_level, which may be 0.
- * Because this memory is allocated in large blocks associated with
- * a given level it can be freed easily at the end of a block.
- */
-typedef struct memory_block {
-       void    *start;                 /* beginning of memory block */
-       void    *first_free;            /* first free byte */
-       size_t  nfree;                  /* # of free bytes */
-       struct  memory_block *next;
-} memory_block;
+/* Array of memory pools, indexed by mem_block_level. */
+typedef struct memory_pools {
+       struct memory_pool *pools;
+       size_t  cap;
+} memory_pools;
 
-
-static size_t  mblk_size;      /* size of newly allocated memory blocks */
+static memory_pools mpools;
 
-/* Array of lists of memory blocks, indexed by mem_block_level. */
-static memory_block    **mblks;
-static size_t  nmblks;         /* number of elements in *mblks */
-#define        ML_INC  ((size_t)32)    /* Increment for length of *mblks */
-
+/* The pool for the current expression is independent of any block level. */
+static memory_pool expr_pool;
 
-/* Allocate new memory, initialized with zero. */
-static void *
-xgetblk(memory_block **mbp, size_t s)
+static void
+mpool_add(memory_pool *pool, void *item)
 {
-       memory_block    *mb;
-       void    *p;
-
-       size_t worst_align = 2 * sizeof(long) - 1;
-       s = (s + worst_align) & ~worst_align;
 
-       if ((mb = *mbp) == NULL || mb->nfree < s) {
-               size_t block_size = s > mblk_size ? s : mblk_size;
-               mb = xmalloc(sizeof(*mb));
-               mb->start = xmalloc(block_size);
-               mb->first_free = mb->start;
-               mb->nfree = block_size;
-               mb->next = *mbp;
-               *mbp = mb;
+       if (pool->len >= pool->cap) {
+               pool->cap = 2 * pool->len + 16;
+               pool->items = xrealloc(pool->items,
+                   sizeof(*pool->items) * pool->cap);
        }
-
-       p = mb->first_free;
-       mb->first_free = (char *)mb->first_free + s;
-       mb->nfree -= s;
-       (void)memset(p, 0, s);
-       return p;
+       pool->items[pool->len++] = item;
 }
 
-/* Free all blocks from list *fmbp. */
 static void
-xfreeblk(memory_block **fmbp)
+mpool_free(memory_pool *pool)
 {
-       memory_block    *mb;
 
-       while ((mb = *fmbp) != NULL) {
-               *fmbp = mb->next;
-               free(mb);
-       }
+       for (; pool->len > 0; pool->len--)
+               free(pool->items[pool->len - 1]);
 }
 
-void
-initmem(void)
+static void *
+mpool_zero_alloc(memory_pool *pool, size_t size)
 {
 
-       mblk_size = mem_block_size();
-       mblks = xcalloc(nmblks = ML_INC, sizeof(*mblks));
+       void *mem = xmalloc(size);
+       memset(mem, 0, size);
+       mpool_add(pool, mem);
+       return mem;
+}