diff --git a/src/conf.h b/src/conf.h
index 93c8d44f..8484cc65 100644
--- a/src/conf.h
+++ b/src/conf.h
@@ -298,10 +298,15 @@ typedef RETSIGTYPE (SIGTYPEENTRY *sig_type)(int);
 #define index               upx_index
 #define outp                upx_outp
 
+
 // a dummy statement
 #define nop     ((void)0)
 
 
+#define COMPILE_TIME_ASSERT(expr) \
+    { typedef int upx_compile_time_assert_fail[(expr) ? 1 : -1]; }
+
+
 /*************************************************************************
 // file io
 **************************************************************************/
diff --git a/src/main.cpp b/src/main.cpp
index 60dbbc9f..c78f583a 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -931,20 +931,20 @@ static void first_options(int argc, char **argv)
 
 void upx_sanity_check(void)
 {
-    assert(sizeof(char) == 1);
-    assert(sizeof(short) == 2);
-    assert(sizeof(int) == 4);
-    assert(sizeof(long) >= 4);
-    assert(sizeof(void *) >= 4);
-    assert(sizeof(long) >= sizeof(void *));
-    assert(((size_t) -1) > 0);
-    assert(((ptrdiff_t) -1) < 0);
-    assert(((off_t) -1) < 0);
+    COMPILE_TIME_ASSERT(sizeof(char) == 1);
+    COMPILE_TIME_ASSERT(sizeof(short) == 2);
+    COMPILE_TIME_ASSERT(sizeof(int) == 4);
+    COMPILE_TIME_ASSERT(sizeof(long) >= 4);
+    COMPILE_TIME_ASSERT(sizeof(void *) >= 4);
+    COMPILE_TIME_ASSERT(sizeof(long) >= sizeof(void *));
+    COMPILE_TIME_ASSERT(((size_t) -1) > 0);
+    COMPILE_TIME_ASSERT(((ptrdiff_t) -1) < 0);
+    COMPILE_TIME_ASSERT(((off_t) -1) < 0);
 
-    assert(sizeof(BE16) == 2);
-    assert(sizeof(BE32) == 4);
-    assert(sizeof(LE16) == 2);
-    assert(sizeof(LE32) == 4);
+    COMPILE_TIME_ASSERT(sizeof(BE16) == 2);
+    COMPILE_TIME_ASSERT(sizeof(BE32) == 4);
+    COMPILE_TIME_ASSERT(sizeof(LE16) == 2);
+    COMPILE_TIME_ASSERT(sizeof(LE32) == 4);
 
     struct align_assertion_1a_t
     {
@@ -978,10 +978,10 @@ void upx_sanity_check(void)
     //printf("%d\n", (int) sizeof(align_assertion_1b_t));
     //printf("%d\n", (int) sizeof(align_assertion_2a_t));
     //printf("%d\n", (int) sizeof(align_assertion_2b_t));
-    assert(sizeof(align_assertion_1a_t) == sizeof(align_assertion_1b_t));
-    assert(sizeof(align_assertion_2a_t) == sizeof(align_assertion_2b_t));
-    assert(sizeof(align_assertion_1a_t) == 3*9);
-    assert(sizeof(align_assertion_2a_t) == 3*17);
+    COMPILE_TIME_ASSERT(sizeof(align_assertion_1a_t) == sizeof(align_assertion_1b_t));
+    COMPILE_TIME_ASSERT(sizeof(align_assertion_2a_t) == sizeof(align_assertion_2b_t));
+    COMPILE_TIME_ASSERT(sizeof(align_assertion_1a_t) == 3*9);
+    COMPILE_TIME_ASSERT(sizeof(align_assertion_2a_t) == 3*17);
 }
 
 
diff --git a/src/p_djgpp2.cpp b/src/p_djgpp2.cpp
index 55fd21f2..a8483815 100644
--- a/src/p_djgpp2.cpp
+++ b/src/p_djgpp2.cpp
@@ -45,8 +45,8 @@ static const
 PackDjgpp2::PackDjgpp2(InputFile *f) :
     super(f), coff_offset(0)
 {
-    assert(sizeof(coff_hdr) == 0xa8);
-    assert(sizeof(stubify_stub) == 2048);
+    COMPILE_TIME_ASSERT(sizeof(coff_hdr) == 0xa8);
+    COMPILE_TIME_ASSERT(sizeof(stubify_stub) == 2048);
 }
 
 
diff --git a/src/p_exe.cpp b/src/p_exe.cpp
index 90f5b300..380f7d7b 100644
--- a/src/p_exe.cpp
+++ b/src/p_exe.cpp
@@ -47,7 +47,7 @@ static const
 PackExe::PackExe(InputFile *f) :
     super(f)
 {
-    assert(sizeof(exe_header_t) == 32);
+    COMPILE_TIME_ASSERT(sizeof(exe_header_t) == 32);
     ih_exesize = ih_imagesize = ih_overlay = 0;
 }
 
diff --git a/src/p_lx_elf.cpp b/src/p_lx_elf.cpp
index f9aaf1d9..a237794a 100644
--- a/src/p_lx_elf.cpp
+++ b/src/p_lx_elf.cpp
@@ -152,7 +152,7 @@ void PackLinuxI386elf::patchLoader()
 bool PackLinuxI386elf::canPack()
 {
     unsigned char buf[sizeof(Elf_LE32_Ehdr) + 14*sizeof(Elf_LE32_Phdr)];
-    assert(sizeof(buf) <= 512);
+    COMPILE_TIME_ASSERT(sizeof(buf) <= 512);
 
     exetype = 0;
 
diff --git a/src/p_tmt.cpp b/src/p_tmt.cpp
index 79cc9aad..a4be8b56 100644
--- a/src/p_tmt.cpp
+++ b/src/p_tmt.cpp
@@ -41,6 +41,12 @@ static const
 //
 **************************************************************************/
 
+PackTmt::PackTmt(InputFile *f) : super(f)
+{
+    COMPILE_TIME_ASSERT(sizeof(tmt_header_t) == 44);
+}
+
+
 int PackTmt::getCompressionMethod() const
 {
     if (M_IS_NRV2B(opt->method))
diff --git a/src/p_tmt.h b/src/p_tmt.h
index 7c5bb1a8..762d2198 100644
--- a/src/p_tmt.h
+++ b/src/p_tmt.h
@@ -38,7 +38,7 @@ class PackTmt : public Packer
 {
     typedef Packer super;
 public:
-    PackTmt(InputFile *f) : super(f) { assert(sizeof(tmt_header_t) == 44); }
+    PackTmt(InputFile *f);
     virtual int getVersion() const { return 11; }
     virtual int getFormat() const { return UPX_F_TMT_ADAM; }
     virtual const char *getName() const { return "tmt/adam"; }
@@ -64,7 +64,7 @@ protected:
         LE32 entry;
         char ___[12];   // esp,numfixups,flags
         LE32 relocsize;
-    } ih,oh;
+    } ih, oh;
 };
 
 
diff --git a/src/p_tos.cpp b/src/p_tos.cpp
index 2732b618..781e826b 100644
--- a/src/p_tos.cpp
+++ b/src/p_tos.cpp
@@ -53,7 +53,7 @@ static const
 PackTos::PackTos(InputFile *f) :
     super(f)
 {
-    assert(FH_SIZE == 28);
+    COMPILE_TIME_ASSERT(FH_SIZE == 28);
 }
 
 
diff --git a/src/p_unix.cpp b/src/p_unix.cpp
index d2376b58..b3e2bd2c 100644
--- a/src/p_unix.cpp
+++ b/src/p_unix.cpp
@@ -44,10 +44,10 @@
 PackUnix::PackUnix(InputFile *f) :
     super(f), exetype(0), blocksize(0), overlay_offset(0), lsize(0)
 {
-    assert(sizeof(Elf_LE32_Ehdr) == 52);
-    assert(sizeof(Elf_LE32_Phdr) == 32);
-    assert(sizeof(l_info) == 12);
-    assert(sizeof(p_info) == 12);
+    COMPILE_TIME_ASSERT(sizeof(Elf_LE32_Ehdr) == 52);
+    COMPILE_TIME_ASSERT(sizeof(Elf_LE32_Phdr) == 32);
+    COMPILE_TIME_ASSERT(sizeof(l_info) == 12);
+    COMPILE_TIME_ASSERT(sizeof(p_info) == 12);
 }
 
 
diff --git a/src/p_vmlinz.cpp b/src/p_vmlinz.cpp
index 63632bc3..cde74a76 100644
--- a/src/p_vmlinz.cpp
+++ b/src/p_vmlinz.cpp
@@ -52,7 +52,7 @@ static const unsigned bzimage_offset = 0x100000;
 PackVmlinuzI386::PackVmlinuzI386(InputFile *f) :
     super(f)
 {
-    assert(sizeof(boot_sect_t) == 0x218);
+    COMPILE_TIME_ASSERT(sizeof(boot_sect_t) == 0x218);
 }
 
 
@@ -88,9 +88,12 @@ int PackVmlinuzI386::readFileHeader()
 {
     boot_sect_t h;
 
+    setup_size = 0;
+
     fi->readx(&h, sizeof(h));
     if (h.boot_flag != 0xAA55)
         return 0;
+    const bool hdrs = (memcmp(h.hdrs, "HdrS", 4) == 0);
 
     setup_size = (1 + (h.setup_sects ? h.setup_sects : 4)) * 0x200;
     if (setup_size <= 0 || setup_size >= file_size)
@@ -98,14 +101,21 @@ int PackVmlinuzI386::readFileHeader()
 
     int format = UPX_F_VMLINUZ_i386;
     unsigned sys_size = ALIGN_UP(file_size, 16) - setup_size;
-    if (memcmp(h.hdrs, "HdrS", 4) == 0 && (h.load_flags & 1) != 0)
+
+    const unsigned char *p = (const unsigned char *) &h + 0x1e3;
+
+    if (hdrs && memcmp(p, "\x0d\x0a\x07""ELKS", 7) == 0)
+    {
+        format = UPX_F_ELKS_8086;
+    }
+    else if (hdrs && (h.load_flags & 1) != 0)
     {
         format = UPX_F_BVMLINUZ_i386;
-        // account for 16-bit h.sys_size, wraparound at 20 bits
+        // account for 16-bit h.sys_size, wrap around at 20 bits
         sys_size &= (1 << 20) - 1;
     }
 
-    if (16 * h.sys_size != sys_size)
+    if (16u * h.sys_size != sys_size)
         return 0;
 
     // FIXME: add more checks for a valid kernel
@@ -160,7 +170,7 @@ void PackVmlinuzI386::readKernel()
     if (klen <= 0)
         throwCantPack("kernel decompression failed");
     if (klen >= (int) ibuf.getSize())
-        throwCantPack("kernel decompression failed -- too big");
+        throwCantPack("kernel decompression failed -- too big; send a bug report");
 
     //OutputFile::dump("kernel.img", ibuf, klen);
 
@@ -233,7 +243,7 @@ void PackVmlinuzI386::pack(OutputFile *fo)
     patch_le32(loader, lsize, "KEIP", kernel_entry);
     patch_le32(loader, lsize, "STAK", stack_during_uncompression);
 
-    boot_sect_t *bs = (boot_sect_t *) ((unsigned char *) setup_buf);
+    boot_sect_t * const bs = (boot_sect_t *) ((unsigned char *) setup_buf);
     bs->sys_size = ALIGN_UP(lsize + ph.c_len, 16) / 16;
 
     fo->write(setup_buf, setup_buf.getSize());
@@ -332,8 +342,8 @@ void PackBvmlinuzI386::pack(OutputFile *fo)
     patch_le32(loader, e_len, "KEIP", kernel_entry);
     patch_le32(loader, e_len, "STAK", stack_during_uncompression);
 
-    boot_sect_t *bs = (boot_sect_t *) ((unsigned char *) setup_buf);
-    bs->sys_size = ALIGN_UP(lsize + clen, 16) / 16;
+    boot_sect_t * const bs = (boot_sect_t *) ((unsigned char *) setup_buf);
+    bs->sys_size = (ALIGN_UP(lsize + clen, 16) / 16) & 0xffff;
 
     fo->write(setup_buf, setup_buf.getSize());
     fo->write(loader, e_len);
diff --git a/src/p_w32pe.cpp b/src/p_w32pe.cpp
index 7a52ee1c..b204281e 100644
--- a/src/p_w32pe.cpp
+++ b/src/p_w32pe.cpp
@@ -64,8 +64,8 @@ PackW32Pe::PackW32Pe(InputFile *f) : super(f)
 {
     //printf("pe_header_t %d\n", (int) sizeof(pe_header_t));
     //printf("pe_section_t %d\n", (int) sizeof(pe_section_t));
-    assert(sizeof(pe_header_t) == 248);
-    assert(sizeof(pe_section_t) == 40);
+    COMPILE_TIME_ASSERT(sizeof(pe_header_t) == 248);
+    COMPILE_TIME_ASSERT(sizeof(pe_section_t) == 40);
 
     isection = 0;
     oimport = 0;
@@ -1204,8 +1204,9 @@ void Resource::clear(upx_byte *node,unsigned level,Interval *iv)
     else
     {
         const res_dir * const rd = (res_dir*) node;
+        const unsigned n = rd->identr + rd->namedentr;
         const res_dir_entry *rde = rd->entries;
-        for (unsigned ic = 0; ic < rd->identr + rd->namedentr; ic++, rde++)
+        for (unsigned ic = 0; ic < n; ic++, rde++)
             clear(newstart + (rde->child & 0x7fffffff),level + 1,iv);
         iv->add(rd,rd->Sizeof());
     }